Shibam owes its fame to its distinct architecture, which is now a UNESCO World Heritage Site. The houses of Shibam are all made out of mud brick but about 500 of them are tower houses, which rise 5 to 11 stories high, with each floor having one or two apartments. This building technique was implemented in order to protect residents from Bedouin attacks. While Shibam has been in existence for an estimated 1,700 years, most of the city’s houses originate from the 16th century. Many, though, have been rebuilt numerous times in the last few centuries.