The 20 meters tall brick tower was built in the 12th-century. It is the tomb of Tuğrul Beg, the founder of the Seljuk Empire who died in Rey in 1063. Originally, like other monuments of its time, it was capped by a conical dome, which would have added to its height. The dome collapsed during an earthquake.
The thickness of the walls varies from 1.75 to 2.75 meters. The inner and outer diameters are 11 and 16 meters, respectively. The exterior shape is that of a polygon with 24 angles in its design, which is thought to contribute to the structure’s stability against tremors.
The main feature of the tower is that its architectural expression is not based on decoration but on mass, which distinguishes it from most medieval brick buildings in Iran.