Mudbrick Houses, Shibam, Yemen, 2005Photograph by George SteinmetzThe city of Shibam, Yemen, rises from the Rub al Khali, or Empty Quarter, a sea of sand that occupies one-fifth of the Arabian Peninsula. The distinctive mud-brick skyscrapers that house Shibam's 5,000 residents have earned the city its nickname: "Manhattan of the Desert."