Al-Ukhaidir combines Late Antique Sasanian engineering with early Islamic planning inside an outer curtain wall measuring 175 by 169 meters with 48 semicircular buttress towers. The three-story inner palace includes a grand reception iwan with a soaring parabolic vault, four self-contained residential units (bayts), an integrated mosque with two mihrabs in its qibla wall, deep underground cellars (sardabs), and some of the earliest surviving Islamic pointed arches and squinches. For more: Al-Ukhaidir Fortress: Guide to Karbala's 8th-Century Abbasid Desert Castle