The history of architecture in Yemen begins in ancient times, when a tradition of South Arabian architecture flourished in the region thanks to the rise of city states that grew wealthy on trade. Developments continued during the Islamic period, displaying both local characteristics and external influences. The historic cities and towns of Yemen are also famous for their traditional tower-houses, built of mud-brick or stone and rising to several stories tall. The old cities of Sana'a, Shibam, and Zabid are designated as UNESCO World Heritage Sites.
