O
- Oaks. (1)
- Office buildings. (270)
- Office equipment & supplies. (16)
- Office workers. (34)
- Officers' quarters. (10)
- Offices. (229)
- Official residences. (192)
- Oil wells. (1)
- Operating rooms. (2)
- Orchestras. (3)
- Ordnance industry. (6)
- Organizations' buildings. (3)
- Organizations' facilities. (239)
- Organizations. (1067)
- Organs. (8)
- Outbuildings. (5)
- Outdoor furniture. (1)
- Ovens. (2)
- Owls. (5)
- Ox teams. (3)