Sana'a, also spelt Sanaa, is the capital of Yemen and the centre of San‘a’ Governorate. Sana'a is one of the oldest continuously inhabited cities in the world. At an altitude of 2,300 metres (7,500 ft), it is also one of the highest capital cities in the world. Sana'a has a population of approximately 1,748,000 (2010) making it Yemen's largest city. The old city of Sana'a, a UNESCO World Heritage Site, has a distinctive visual character due its unique architectural characteristics, most notably expressed in its multi-story buildings decorated with geometric patterns.