diff --git a/city_model_structure/building.py b/city_model_structure/building.py
new file mode 100644
index 00000000..830f370e
--- /dev/null
+++ b/city_model_structure/building.py
@@ -0,0 +1,317 @@
+"""
+CityObject module
+SPDX - License - Identifier: LGPL - 3.0 - or -later
+Copyright © 2020 Project Author Guille Gutierrez guillermo.gutierrezmorote@concordia.ca
+"""
+from pathlib import Path
+from typing import Union, List
+
+import matplotlib.patches as patches
+import numpy as np
+from matplotlib import pylab
+from shapely import ops
+from shapely.geometry import MultiPolygon
+
+from city_model_structure.polyhedron import Polyhedron
+from city_model_structure.surface import Surface
+from city_model_structure.thermal_boundary import ThermalBoundary
+from city_model_structure.thermal_zone import ThermalZone
+from city_model_structure.usage_zone import UsageZone
+from city_model_structure.city_object import CityObject
+
+
+class Building(CityObject):
+  """
+  CityObject class
+  """
+  def __init__(self, name, lod, surfaces, terrains, year_of_construction, function, lower_corner, attic_heated=0,
+               basement_heated=0):
+    super().__init__(lod)
+    self._name = name
+    self._surfaces = surfaces
+    self._basement_heated = basement_heated
+    self._attic_heated = attic_heated
+    self._terrains = terrains
+    self._year_of_construction = year_of_construction
+    self._function = function
+    self._lower_corner = lower_corner
+    self._average_storey_height = None
+    self._storeys_above_ground = None
+    self._foot_print = None
+    self._usage_zones = []
+    self._type = 'building'
+
+    # ToDo: Check this for LOD4
+    self._thermal_zones = []
+    if self.lod < 8:
+      # for lod under 4 is just one thermal zone
+      self._thermal_zones.append(ThermalZone(self.surfaces))
+
+    for t_zones in self._thermal_zones:
+      t_zones.bounded = [ThermalBoundary(s, [t_zones]) for s in t_zones.surfaces]
+    surface_id = 0
+    for surface in self._surfaces:
+      surface.lower_corner = self._lower_corner
+      surface.parent(self, surface_id)
+      surface_id += 1
+
+  @property
+  def usage_zones(self) -> List[UsageZone]:
+    """
+    Get city object usage zones
+    :return: [UsageZone]
+    """
+    return self._usage_zones
+
+  @usage_zones.setter
+  def usage_zones(self, values):
+    """
+    Set city objects usage zones
+    :param values: [UsageZones]
+    :return: None
+    """
+    # ToDo: this is only valid for one usage zone need to be revised for multiple usage zones.
+    self._usage_zones = values
+    for thermal_zone in self.thermal_zones:
+      thermal_zone.usage_zones = [(100, usage_zone) for usage_zone in values]
+
+  @property
+  def terrains(self) -> List[Surface]:
+    """
+    Get city object terrain surfaces
+    :return: [Surface]
+    """
+    return self._terrains
+
+  @property
+  def attic_heated(self):
+    """
+    Get if the city object attic is heated
+    :return: Boolean
+    """
+    return self._attic_heated
+
+  @attic_heated.setter
+  def attic_heated(self, value):
+    """
+    Set if the city object attic is heated
+    :param value: Boolean
+    :return: None
+    """
+    self._attic_heated = value
+
+  @property
+  def basement_heated(self):
+    """
+    Get if the city object basement is heated
+    :return: Boolean
+    """
+    return self._basement_heated
+
+  @basement_heated.setter
+  def basement_heated(self, value):
+    """
+    Set if the city object basement is heated
+    :param value: Boolean
+    :return: None
+    """
+    self._attic_heated = value
+
+  @property
+  def name(self):
+    """
+    City object name
+    :return: str
+    """
+    return self._name
+
+  @property
+  def lod(self):
+    """
+    City object level of detail 1, 2, 3 or 4
+    :return: int
+    """
+    return self._lod
+
+  @property
+  def surfaces(self) -> List[Surface]:
+    """
+    City object surfaces
+    :return: [Surface]
+    """
+    return self._surfaces
+
+  def surface(self, name) -> Union[Surface, None]:
+    """
+    Get the city object surface with a given name
+    :param name: str
+    :return: None or Surface
+    """
+    for s in self.surfaces:
+      if s.name == name:
+        return s
+    return None
+
+  @property
+  def thermal_zones(self) -> List[ThermalZone]:
+    """
+    City object thermal zones
+    :return: [ThermalZone]
+    """
+    return self._thermal_zones
+
+  @property
+  def volume(self):
+    """
+    City object volume in cubic meters
+    :return: float
+    """
+    if self._polyhedron is None:
+      self._polyhedron = Polyhedron(self.surfaces)
+    return self._polyhedron.volume
+
+  @property
+  def heated_volume(self):
+    """
+    City object heated volume in cubic meters
+    :return: float
+    """
+    if self._polyhedron is None:
+      self._polyhedron = Polyhedron(self.surfaces)
+    # ToDo: this need to be the calculated based on the basement and attic heated values
+    return self._polyhedron.volume
+
+  def stl_export(self, path):
+    """
+    Export the city object to stl file (city_object_name.stl) to the given path
+    :param path: str
+    :return: None
+    """
+    # todo: this is a method just for debugging, it will be soon removed
+    if self._polyhedron is None:
+      self._polyhedron = Polyhedron(self.surfaces)
+    full_path = (Path(path) / (self._name + '.stl')).resolve()
+    self._polyhedron.export(full_path)
+
+  @property
+  def year_of_construction(self):
+    """
+    City object year of construction
+    :return: int
+    """
+    return self._year_of_construction
+
+  @property
+  def function(self):
+    """
+    City object function
+    :return: str
+    """
+    return self._function
+
+  @property
+  def average_storey_height(self):
+    """
+    Get city object average storey height in meters
+    :return: float
+    """
+    return self._average_storey_height
+
+  @average_storey_height.setter
+  def average_storey_height(self, value):
+    """
+    Set city object average storey height in meters
+    :param value: float
+    :return: None
+    """
+    self._average_storey_height = value
+
+  @property
+  def storeys_above_ground(self):
+    """
+    Get city object storeys number above ground
+    :return: int
+    """
+    return self._storeys_above_ground
+
+  @storeys_above_ground.setter
+  def storeys_above_ground(self, value):
+    """
+    Set city object storeys number above ground
+    :param value: int
+    :return:
+    """
+    self._storeys_above_ground = value
+
+  @staticmethod
+  def _tuple_to_point(xy_tuple):
+    return [xy_tuple[0], xy_tuple[1], 0.0]
+
+  def _plot(self, polygon):
+    points = ()
+    for point_tuple in polygon.exterior.coords:
+      almost_equal = False
+      for point in points:
+        point_1 = Building._tuple_to_point(point)
+        point_2 = Building._tuple_to_point(point_tuple)
+        if self._geometry.almost_equal(point_1, point_2):
+          almost_equal = True
+          break
+      if not almost_equal:
+        points = points + (point_tuple,)
+    points = points + (points[0],)
+    pylab.scatter([point[0] for point in points], [point[1] for point in points])
+    pylab.gca().add_patch(patches.Polygon(points, closed=True, fill=True))
+    pylab.grid()
+    pylab.show()
+
+  @property
+  def foot_print(self) -> Surface:
+    """
+    City object foot print surface
+    :return: Surface
+    """
+    if self._foot_print is None:
+      shapelys = []
+      union = None
+      for surface in self.surfaces:
+        if surface.shapely.is_empty or not surface.shapely.is_valid:
+          continue
+        shapelys.append(surface.shapely)
+        union = ops.unary_union(shapelys)
+        shapelys = [union]
+      if isinstance(union, MultiPolygon):
+        Exception('foot print returns a multipolygon')
+      points_list = []
+      for point_tuple in union.exterior.coords:
+        # ToDo: should be Z 0.0 or min Z?
+        point = Building._tuple_to_point(point_tuple)
+        almost_equal = False
+        for existing_point in points_list:
+          if self._geometry.almost_equal(point, existing_point):
+            almost_equal = True
+            break
+        if not almost_equal:
+          points_list.append(point)
+      points_list = np.reshape(points_list, len(points_list) * 3)
+      points = np.array_str(points_list).replace('[', '').replace(']', '')
+      self._foot_print = Surface(points, remove_last=False, is_projected=True)
+    return self._foot_print
+
+  @property
+  def type(self):
+    """
+    City object type
+    :return: str
+    """
+    return self._type
+
+  @property
+  def max_height(self):
+    """
+    City object maximal height in meters
+    :return: float
+    """
+    if self._polyhedron is None:
+      self._polyhedron = Polyhedron(self.surfaces)
+    return self._polyhedron.max_z
diff --git a/city_model_structure/city.py b/city_model_structure/city.py
index 1fe3a69c..f12cc89f 100644
--- a/city_model_structure/city.py
+++ b/city_model_structure/city.py
@@ -10,6 +10,7 @@ import pyproj
 import reverse_geocoder as rg
 from pyproj import Transformer
 
+from city_model_structure.building import Building
 from city_model_structure.city_object import CityObject
 
 
@@ -18,12 +19,12 @@ class City:
   City class
   """
 
-  def __init__(self, lower_corner, upper_corner, srs_name, city_objects=None):
-    self._city_objects = None
+  def __init__(self, lower_corner, upper_corner, srs_name, buildings=None):
+    self._buildings = None
     self._name = None
     self._lower_corner = lower_corner
     self._upper_corner = upper_corner
-    self._city_objects = city_objects
+    self._buildings = buildings
     self._srs_name = srs_name
     # todo: right now extracted at city level, in the future should be extracted also at building level if exist
     self._location = None
@@ -62,10 +63,42 @@ class City:
   @property
   def city_objects(self) -> Union[List[CityObject], None]:
     """
-    CityObjects belonging to the city
-    :return: None or a list of CityObjects
+    City objects belonging to the city
+    :return: None or [CityObject]
     """
-    return self._city_objects
+    return self.buildings
+
+  @property
+  def buildings(self) -> Union[List[Building], None]:
+    """
+    Buildings belonging to the city
+    :return: None or [Building]
+    """
+    return self._buildings
+
+  @property
+  def trees(self) -> NotImplementedError:
+    """
+    Trees belonging to the city
+    :return: NotImplementedError
+    """
+    raise NotImplementedError
+
+  @property
+  def bixi_features(self) -> NotImplementedError:
+    """
+    Bixi features belonging to the city
+    :return: NotImplementedError
+    """
+    raise NotImplementedError
+
+  @property
+  def composting_plants(self) -> NotImplementedError:
+    """
+    Composting plants belonging to the city
+    :return: NotImplementedError
+    """
+    raise NotImplementedError
 
   @property
   def lower_corner(self):
@@ -89,7 +122,7 @@ class City:
     :param name:str
     :return: None or CityObject
     """
-    for city_object in self.city_objects:
+    for city_object in self.buildings:
       if city_object.name == name:
         return city_object
     return None
@@ -100,13 +133,15 @@ class City:
     :param new_city_object:CityObject
     :return: None
     """
-    if self._city_objects is None:
-      self._city_objects = []
-    for city_object in self.city_objects:
-      for surface in city_object.surfaces:
+    if new_city_object.type != 'building':
+      raise NotImplementedError(new_city_object.type)
+    if self._buildings is None:
+      self._buildings = []
+    for building in self.buildings:
+      for surface in building.surfaces:
         for surface2 in new_city_object.surfaces:
           surface.shared(surface2)
-    self._city_objects.append(new_city_object)
+    self._buildings.append(new_city_object)
 
   @property
   def srs_name(self):
diff --git a/city_model_structure/city_object.py b/city_model_structure/city_object.py
index 3e2a599e..7a368d16 100644
--- a/city_model_structure/city_object.py
+++ b/city_model_structure/city_object.py
@@ -1,320 +1,8 @@
-"""
-CityObject module
-SPDX - License - Identifier: LGPL - 3.0 - or -later
-Copyright © 2020 Project Author Guille Gutierrez guillermo.gutierrezmorote@concordia.ca
-"""
-from pathlib import Path
-from typing import Union, List
-
-import matplotlib.patches as patches
-import numpy as np
-from matplotlib import pylab
-from shapely import ops
-from shapely.geometry import MultiPolygon
-
-from city_model_structure.polyhedron import Polyhedron
-from city_model_structure.surface import Surface
-from city_model_structure.thermal_boundary import ThermalBoundary
-from city_model_structure.thermal_zone import ThermalZone
-from city_model_structure.usage_zone import UsageZone
 from helpers.geometry_helper import GeometryHelper
 
 
 class CityObject:
-  """
-  CityObject class
-  """
-  def __init__(self, name, lod, surfaces, terrains, year_of_construction, function, lower_corner, attic_heated=0,
-               basement_heated=0):
-    self._name = name
+  def __init__(self, lod):
     self._lod = lod
-    self._surfaces = surfaces
     self._polyhedron = None
-    self._basement_heated = basement_heated
-    self._attic_heated = attic_heated
-    self._terrains = terrains
-    self._year_of_construction = year_of_construction
-    self._function = function
-    self._lower_corner = lower_corner
     self._geometry = GeometryHelper()
-    self._average_storey_height = None
-    self._storeys_above_ground = None
-    self._foot_print = None
-    self._usage_zones = []
-    # ToDo: this need to be changed when we have other city_objects beside "buildings"
-    self._type = 'building'
-
-    # ToDo: Check this for LOD4
-    self._thermal_zones = []
-    if self.lod < 8:
-      # for lod under 4 is just one thermal zone
-      self._thermal_zones.append(ThermalZone(self.surfaces))
-
-    for t_zones in self._thermal_zones:
-      t_zones.bounded = [ThermalBoundary(s, [t_zones]) for s in t_zones.surfaces]
-    surface_id = 0
-    for surface in self._surfaces:
-      surface.lower_corner = self._lower_corner
-      surface.parent(self, surface_id)
-      surface_id += 1
-
-  @property
-  def usage_zones(self) -> List[UsageZone]:
-    """
-    Get city object usage zones
-    :return: [UsageZone]
-    """
-    return self._usage_zones
-
-  @usage_zones.setter
-  def usage_zones(self, values):
-    """
-    Set city objects usage zones
-    :param values: [UsageZones]
-    :return: None
-    """
-    # ToDo: this is only valid for one usage zone need to be revised for multiple usage zones.
-    self._usage_zones = values
-    for thermal_zone in self.thermal_zones:
-      thermal_zone.usage_zones = [(100, usage_zone) for usage_zone in values]
-
-  @property
-  def terrains(self) -> List[Surface]:
-    """
-    Get city object terrain surfaces
-    :return: [Surface]
-    """
-    return self._terrains
-
-  @property
-  def attic_heated(self):
-    """
-    Get if the city object attic is heated
-    :return: Boolean
-    """
-    return self._attic_heated
-
-  @attic_heated.setter
-  def attic_heated(self, value):
-    """
-    Set if the city object attic is heated
-    :param value: Boolean
-    :return: None
-    """
-    self._attic_heated = value
-
-  @property
-  def basement_heated(self):
-    """
-    Get if the city object basement is heated
-    :return: Boolean
-    """
-    return self._basement_heated
-
-  @basement_heated.setter
-  def basement_heated(self, value):
-    """
-    Set if the city object basement is heated
-    :param value: Boolean
-    :return: None
-    """
-    self._attic_heated = value
-
-  @property
-  def name(self):
-    """
-    City object name
-    :return: str
-    """
-    return self._name
-
-  @property
-  def lod(self):
-    """
-    City object level of detail 1, 2, 3 or 4
-    :return: int
-    """
-    return self._lod
-
-  @property
-  def surfaces(self) -> List[Surface]:
-    """
-    City object surfaces
-    :return: [Surface]
-    """
-    return self._surfaces
-
-  def surface(self, name) -> Union[Surface, None]:
-    """
-    Get the city object surface with a given name
-    :param name: str
-    :return: None or Surface
-    """
-    for s in self.surfaces:
-      if s.name == name:
-        return s
-    return None
-
-  @property
-  def thermal_zones(self) -> List[ThermalZone]:
-    """
-    City object thermal zones
-    :return: [ThermalZone]
-    """
-    return self._thermal_zones
-
-  @property
-  def volume(self):
-    """
-    City object volume in cubic meters
-    :return: float
-    """
-    if self._polyhedron is None:
-      self._polyhedron = Polyhedron(self.surfaces)
-    return self._polyhedron.volume
-
-  @property
-  def heated_volume(self):
-    """
-    City object heated volume in cubic meters
-    :return: float
-    """
-    if self._polyhedron is None:
-      self._polyhedron = Polyhedron(self.surfaces)
-    # ToDo: this need to be the calculated based on the basement and attic heated values
-    return self._polyhedron.volume
-
-  def stl_export(self, path):
-    """
-    Export the city object to stl file (city_object_name.stl) to the given path
-    :param path: str
-    :return: None
-    """
-    # todo: this is a method just for debugging, it will be soon removed
-    if self._polyhedron is None:
-      self._polyhedron = Polyhedron(self.surfaces)
-    full_path = (Path(path) / (self._name + '.stl')).resolve()
-    self._polyhedron.export(full_path)
-
-  @property
-  def year_of_construction(self):
-    """
-    City object year of construction
-    :return: int
-    """
-    return self._year_of_construction
-
-  @property
-  def function(self):
-    """
-    City object function
-    :return: str
-    """
-    return self._function
-
-  @property
-  def average_storey_height(self):
-    """
-    Get city object average storey height in meters
-    :return: float
-    """
-    return self._average_storey_height
-
-  @average_storey_height.setter
-  def average_storey_height(self, value):
-    """
-    Set city object average storey height in meters
-    :param value: float
-    :return: None
-    """
-    self._average_storey_height = value
-
-  @property
-  def storeys_above_ground(self):
-    """
-    Get city object storeys number above ground
-    :return: int
-    """
-    return self._storeys_above_ground
-
-  @storeys_above_ground.setter
-  def storeys_above_ground(self, value):
-    """
-    Set city object storeys number above ground
-    :param value: int
-    :return:
-    """
-    self._storeys_above_ground = value
-
-  @staticmethod
-  def _tuple_to_point(xy_tuple):
-    return [xy_tuple[0], xy_tuple[1], 0.0]
-
-  def _plot(self, polygon):
-    points = ()
-    for point_tuple in polygon.exterior.coords:
-      almost_equal = False
-      for point in points:
-        point_1 = CityObject._tuple_to_point(point)
-        point_2 = CityObject._tuple_to_point(point_tuple)
-        if self._geometry.almost_equal(point_1, point_2):
-          almost_equal = True
-          break
-      if not almost_equal:
-        points = points + (point_tuple,)
-    points = points + (points[0],)
-    pylab.scatter([point[0] for point in points], [point[1] for point in points])
-    pylab.gca().add_patch(patches.Polygon(points, closed=True, fill=True))
-    pylab.grid()
-    pylab.show()
-
-  @property
-  def foot_print(self) -> Surface:
-    """
-    City object foot print surface
-    :return: Surface
-    """
-    if self._foot_print is None:
-      shapelys = []
-      union = None
-      for surface in self.surfaces:
-        if surface.shapely.is_empty or not surface.shapely.is_valid:
-          continue
-        shapelys.append(surface.shapely)
-        union = ops.unary_union(shapelys)
-        shapelys = [union]
-      if isinstance(union, MultiPolygon):
-        Exception('foot print returns a multipolygon')
-      points_list = []
-      for point_tuple in union.exterior.coords:
-        # ToDo: should be Z 0.0 or min Z?
-        point = CityObject._tuple_to_point(point_tuple)
-        almost_equal = False
-        for existing_point in points_list:
-          if self._geometry.almost_equal(point, existing_point):
-            almost_equal = True
-            break
-        if not almost_equal:
-          points_list.append(point)
-      points_list = np.reshape(points_list, len(points_list) * 3)
-      points = np.array_str(points_list).replace('[', '').replace(']', '')
-      self._foot_print = Surface(points, remove_last=False, is_projected=True)
-    return self._foot_print
-
-  @property
-  def type(self):
-    """
-    City object type
-    :return: str
-    """
-    return self._type
-
-  @property
-  def max_height(self):
-    """
-    City object maximal height in meters
-    :return: float
-    """
-    if self._polyhedron is None:
-      self._polyhedron = Polyhedron(self.surfaces)
-    return self._polyhedron.max_z
diff --git a/city_model_structure/thermal_opening.py b/city_model_structure/thermal_opening.py
index f5ab59a9..3ed23816 100644
--- a/city_model_structure/thermal_opening.py
+++ b/city_model_structure/thermal_opening.py
@@ -26,7 +26,7 @@ class ThermalOpening:
     Get thermal opening openable ratio, NOT IMPLEMENTED
     :return: Exception
     """
-    raise Exception('Not implemented')
+    raise NotImplementedError()
 
   @openable_ratio.setter
   def openable_ratio(self, value):
@@ -35,7 +35,7 @@ class ThermalOpening:
     :param value: Any
     :return: Exception
     """
-    raise Exception('Not implemented')
+    raise NotImplementedError()
 
   @property
   def conductivity(self):
diff --git a/geometry/geometry_feeders/city_gml.py b/geometry/geometry_feeders/city_gml.py
index 1fa2b6fe..b801c965 100644
--- a/geometry/geometry_feeders/city_gml.py
+++ b/geometry/geometry_feeders/city_gml.py
@@ -7,7 +7,7 @@ import numpy as np
 import xmltodict
 
 from city_model_structure.city import City
-from city_model_structure.city_object import CityObject
+from city_model_structure.building import Building
 from city_model_structure.surface import Surface
 from helpers.geometry_helper import GeometryHelper
 
@@ -115,6 +115,6 @@ class CityGml:
           year_of_construction = o['Building']['yearOfConstruction']
         if 'function' in o['Building']:
           function = o['Building']['function']
-        self._city.add_city_object(CityObject(name, lod, surfaces, terrains, year_of_construction, function,
-                                              self._lower_corner))
+        self._city.add_city_object(Building(name, lod, surfaces, terrains, year_of_construction, function,
+                                            self._lower_corner))
     return self._city
diff --git a/physics/physics_feeders/us_new_york_city_physics_parameters.py b/physics/physics_feeders/us_new_york_city_physics_parameters.py
index 6e8816df..ed87f819 100644
--- a/physics/physics_feeders/us_new_york_city_physics_parameters.py
+++ b/physics/physics_feeders/us_new_york_city_physics_parameters.py
@@ -14,4 +14,4 @@ class UsNewYorkCityPhysicsParameters(UsBasePhysicsParameters):
   def __init__(self, city, base_path):
     self._city = city
     climate_zone = 'ASHRAE_2004:4A'
-    super().__init__(climate_zone, self._city.city_objects, Pf.function, base_path)
+    super().__init__(climate_zone, self._city.buildings, Pf.function, base_path)
diff --git a/physics/physics_feeders/us_physics_parameters.py b/physics/physics_feeders/us_physics_parameters.py
index 09d15b1a..3630eb30 100644
--- a/physics/physics_feeders/us_physics_parameters.py
+++ b/physics/physics_feeders/us_physics_parameters.py
@@ -14,4 +14,4 @@ class UsPhysicsParameters(UsBasePhysicsParameters):
   def __init__(self, city, base_path):
     self._city = city
     self._climate_zone = UsToLibraryTypes.city_to_climate_zone(city.name)
-    super().__init__(self._climate_zone, self._city.city_objects, lambda function: function, base_path)
+    super().__init__(self._climate_zone, self._city.buildings, lambda function: function, base_path)
diff --git a/tests/test_geometry_factory.py b/tests/test_geometry_factory.py
index 3a2049ed..3af9134e 100644
--- a/tests/test_geometry_factory.py
+++ b/tests/test_geometry_factory.py
@@ -35,8 +35,8 @@ class TestGeometryFactory(TestCase):
     :return: None
     """
     city = self._get_citygml()
-    self.assertIsNotNone(city.city_objects, 'city_objects is none')
-    for city_object in city.city_objects:
+    self.assertIsNotNone(city.buildings, 'city_objects is none')
+    for city_object in city.buildings:
       self.assertIsNotNone(city.city_object(city_object.name), 'city_object return none')
     self.assertIsNotNone(city.srs_name, 'srs_name is none')
     self.assertIsNotNone(city.lower_corner, 'lower_corner is none')
@@ -50,7 +50,7 @@ class TestGeometryFactory(TestCase):
     :return: None
     """
     city = self._get_citygml()
-    for city_object in city.city_objects:
+    for city_object in city.buildings:
       self.assertIsNotNone(city_object.name, 'city_object name is none')
       self.assertIsNotNone(city_object.lod, 'city_object lod is none')
       self.assertIsNotNone(city_object.year_of_construction, 'city_object year_of_construction is none')
@@ -78,7 +78,7 @@ class TestGeometryFactory(TestCase):
     :return: None
     """
     city = self._get_citygml()
-    for city_object in city.city_objects:
+    for city_object in city.buildings:
       for surface in city_object.surfaces:
         self.assertIsNotNone(surface.name, 'surface name is none')
         self.assertIsNotNone(surface.area, 'surface area is none')
@@ -109,7 +109,7 @@ class TestGeometryFactory(TestCase):
     :return: None
     """
     city = self._get_citygml()
-    for city_object in city.city_objects:
+    for city_object in city.buildings:
       for thermal_zone in city_object.thermal_zones:
         self.assertIsNotNone(thermal_zone.surfaces, 'thermal_zone surfaces is none')
         self.assertIsNotNone(thermal_zone.bounded, 'thermal_zone bounded is none')
@@ -135,7 +135,7 @@ class TestGeometryFactory(TestCase):
     :return: None
     """
     city = self._get_citygml()
-    for city_object in city.city_objects:
+    for city_object in city.buildings:
       for thermal_zone in city_object.thermal_zones:
         for thermal_boundary in thermal_zone.bounded:
           self.assertIsNotNone(thermal_boundary.type, 'thermal_boundary type is none')
@@ -165,7 +165,7 @@ class TestGeometryFactory(TestCase):
     :return: None
     """
     city = self._get_citygml()
-    for city_object in city.city_objects:
+    for city_object in city.buildings:
       for thermal_zone in city_object.thermal_zones:
         for thermal_boundary in thermal_zone.bounded:
           for thermal_opening in thermal_boundary.thermal_openings:
diff --git a/tests/test_physics_factory.py b/tests/test_physics_factory.py
index 588e7fad..4395fc10 100644
--- a/tests/test_physics_factory.py
+++ b/tests/test_physics_factory.py
@@ -42,7 +42,7 @@ class TestPhysicsFactory(TestCase):
     :return: None
     """
     city = self._get_city_with_physics()
-    for city_object in city.city_objects:
+    for city_object in city.buildings:
       self.assertIsNotNone(city_object.average_storey_height, 'average_storey_height is none')
       self.assertIsNotNone(city_object.storeys_above_ground, 'storeys_above_ground is none')
       for thermal_zone in city_object.thermal_zones:
diff --git a/usage/usage_feeders/us_base_usage_parameters.py b/usage/usage_feeders/us_base_usage_parameters.py
index ab38bce1..0614ce46 100644
--- a/usage/usage_feeders/us_base_usage_parameters.py
+++ b/usage/usage_feeders/us_base_usage_parameters.py
@@ -21,7 +21,7 @@ class UsBaseUsageParameters:
     path = str(Path.cwd() / 'data/usage/de_library.xml')
     with open(path) as xml:
       self._library = xmltodict.parse(xml.read(), force_list='zoneUsageVariant')
-    for city_object in self._city.city_objects:
+    for city_object in self._city.buildings:
       # ToDo: Right now is just one usage zone but will be multiple in the future
       usage_zone = UsageZone()
       usage_zone.usage = function_to_usage(city_object.function)