Ramlat al-Sab'atayn
The Ramlat al-Sab'atayn is a desert region that corresponds with the northern deserts of modern Yemen and southwestern Saudi Arabia.
It comprises mainly transverse and seif dunes and covers an area of about, roughly.
The Ramlat as Sab'atayn includes part of what was known to medieval Arab geographers as the Sayhad. It extends from al-Khawr to the edge of the Rub' al-Khālī or Empty Quarter. It includes the Yemeni muhafazahs of al-Jawf, Ma'rib and Shabwa.