The Gunbad-i Qabus is a flanged, cylindrical, slightly tapering tower with a conical roof, situated on a small hill. The tomb takes the name of the Ziyarid ruler Qabus b. Voshmgir. Qabus was an astrologer, poet, calligrapher, and patron of numerous scholars and writers, including Ibn Sina (Avicenna) and al-Biruni (Aliboron). He reigned in Gurgan until his assassination in 1012, five years after initiation of the tomb's construction. However, there are other differing accounts as well, which claim that the grave of Qabus cannot be in this gunbadkhanah.

The building is entirely made of bricks. The body of the tower is built of firm, unglazed, fired bricks, which are now rather “weathered and discolored”.  The height of the tower is 37 meters, with a further 18 meter high conical vault. The half-vault of the portal rests on two rows of primitive brick muqarnas. There is no access to the roof, which has a small opening in the eastern side, and no underground chamber. Reports suggest that Qabus' glass coffin was suspended within the dome, the morning sun striking his body through the eastern opening.

The interior is undecorated and without fenestration. On the exterior face, between the ten flanges, are two rows of inscriptions in brick-formed Kufic.

Presently, Mausoloeum of Qabus is the only remaining relic of the ancient city of Gurgan, which flourished as one of the largest academic centers under Ziyarid rule before falling into ruins during the Mongol invasion.