The eastern of two tombs near Radkan, the Mil-i Radkan is located eighty kilometers to the north of Mashhad. Based on epigraphic remnants, Ernst Herzfeld has argued that the tomb tower belongs to Amir Arghun Khan, a residence of Radkan who died in 1274. Due to damages to the exterior fabric of the structure and the loss of epigraphic evidence, an absolute dating of the tomb tower is impossible. Stylistic clues, combined with evidence from existing parts of the inscriptive frieze date this monument between 1280 and 1300.
The tomb is cylindrical, with an octagonal burial chamber crowned by a conical dome. It is entered from two axial entrances facing southeast and northwest. The thirty-six engaged columns enveloping its exterior between the base and the dome give the tomb a wavy outline. A spiraling stair encased within the monument's walls gives access to the inner dome, of which only the base remains. The double dome construction of the roof has a long history in the tomb towers built in Iran during the Seljuk period (roughly 1050-1150) and before. Gunbad-i Qabus in Gurgan is the first example of a monumental tomb structure that employs a double dome construction with an outer conical roof covering an inner hemispherical one.
A variety of brick patterns are used with terracotta and glazed bricks to decorate the exterior. The base of the tomb is made of two horizontal courses of brick alternating with two shorter verticals. A herringbone brick weave mirrored about the centerline decorates the engaged columns. The individual columns are joined with miniature trefoil arches at the top, above which is a frieze of Kufic inscriptions that give the date of construction and the name of the tomb owner. The use of glazed terracotta in the inscriptive frieze as well as in areas within the trefoil arches, locates this monument in the later phases of Seljuk reign in Iran. The interior of the chamber is plain except for brick variations on the transition zone of the dome. The large holes in the chamber walls, the stripped base of the monument and the missing top of the conical roof that are seen in earlier photographs have all been restored.