Situated in a mountain valley at an altitude of 2,200 m, Sana’a 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. This religious and political heritage can be seen in the 103 mosques, 14 hammams and over 6,000 houses, all built before the 11th century. The old city of Sana'a is a world heritage site since 1986 and its wonderful design enchanted travelers, merchants and scholars from the ancient to the present time. A traditional Yemeni saying declaims: "Sana'a must be seen, however long the journey".