Old Walled City of Shibam

Inscribed on the United Nations World Heritage List in 1982.

From http://whc.unesco.org/pg.cfm?cid=31&id_site=192:

Surrounded by a fortified wall, the 16th-century city of Shibam is one of the oldest and best examples of urban planning based on the principle of vertical construction. Its impressive tower-like structures rise out of the cliff and have given the city the nickname of 'the Manhattan of the desert'.