The Mausolea of Saba' Banat are four small structures (there were originally seven) located south of the ruins of Fustat. They date from 1010, and each consisted of a three-story cube with tall domes carried on drums pierced by windows.

The buildings are examples of "canopy tombs:" mausolea whose open sides leave them open to the elements. In these buildings a pointed arch in the center of each façade, windows in the zones of transition, and windows circling the bases of the domes all open the interior of the structures to the elements.

Source

Creswell, K. A. C. 1978. The Muslim Architecture of Egypt. (NY: Hacker), p.107-113.