The mausoleum of Seljuk ruler Ahmad Sanjar (1118 - 57) occupies the center of the ruined walled city of Sultan Kala, Merv. This mud brick mausoleum represents the architectural peak of the destroyed Seljuk capital in the Merv Oasis of the Karakum Desert, along the famed Silk Road. Muhammad ibn Aziz from Sarakhs in Khorasan built the mausoleum soon after the Khwarazm Shahs deposed the Seljuk dynasty. Unlike many of Sultan Kala's solitary tombs, the mausoleum was part of a larger religious and palatial complex and connected by a grille window to a mosque on its west. None of the ancillary buildings survive. The mausoleum is noted as a rare example of Seljuk commemorative architecture dedicated to a non-religious and political figure. It also marks a significant shift, from the typical vertically-accentuated Seljuk tomb tower towards squatter proportions with a new emphasis on interior space.
The mausoleum consists of an enormous brick cube, approximately 27 meters square crowned by a large dome nearly 18 meters in diameter. Arched corner galleries along the upper story maintain a stark rectangular profile while concealing the squinches that mark the cube's transition to the dome. The gallery façade's alternate pointed-arch and triangular-arch bays create solid-void compositions that harmonize with two rows of blind arches along the dome's base. Miniature turrets along each corner above the gallery once facilitated the cube-to-dome transition, but were lost over time.
The mausoleum's square, brick mass is relieved by two gateways, expressed on the east and west elevations. Plaster carved to simulate brick bonds and inset with terracotta panels decorates some brick facades. The elevations also exhibit traces of stucco treatment and holes left behind by scaffolding erected for repeated restoration efforts. The galleries are elaborately adorned with terracotta patterns in arch intrados and alternate panels of carved brickwork. The outer dome was once embellished with turquoise tiles, but only its interior's exposed, interlaced structural ribs exist today. These trace a central eight-pointed star motif within the dome's eye, surrounded by a radial series of foiled arches and stalactite-topped pilasters.
The mausoleum is much revered and has been restored several times. The dome was restored in 1911, and the galleries were largely rebuilt in recent decades. Unfortunately, much of the twelfth-century terracotta ornament is feared to have been lost in insensitive reconstruction projects during the 1990s. The monument and the cultural park of ancient Merv was declared a UNESCO World Heritage site in 1999. World attention and increased tourist inflow have guaranteed better upkeep of the structure.