To the east of the Caravansaray Gate, just outside the confines of Dash Gala, is the fortress known as Ak Gala. Its southern wall ran alongside the old channel of the Amu Darya, making a formidable defensive barrier. The fragments of mud-brick wall which survive along its 1km perimeter reach a height of up to 8m. These probably date to no earlier than the 16th century, but are built on top of earlier walls, destroyed by Timur. Researchers have speculated that this fortress may have been the Keshk-i-Ahchak mentioned by a 13th-century scholar as one of two monuments of Urgench (the other being the Tekesh Mausoleum) not destroyed by the Mongols.