Sana'a, or Sana'a is the largest city in Yemen and the centre of Sana'a Governorate. The city has been inhabited for more than 2,500 years. In the 7th and 8th centuries the city became a major centre for the propagation of Islam. The Great Mosque of Sana'a, built in the 7th century AD, is one of the most important landmarks of the old city. The city was inscribed as a UNESCO World Heritage Site in 1986.