One of numerous tomb towers in Qum, the Imamzade Ali ibn Ja'far traces an octagonal plan both on the exterior and interior. It is crowned with a sixteen-side tent dome, hemispherical on the interior. Polychrome painted plaster with low relief carving decorates the interior surfaces.

Source:

Donald N. Wilber, The Architecture of Islamic Iran: The Il Khanid Period. New York: Greenwood Press, 1969, 132-133