The freestanding structure of Qubbat Yusuf ascends from the southern wall of the Dome of the Rock terrace between Qubbat Nahwiyya and Minbar burhan al-Din. Its founder is referred to in the foundation inscriptions as Yusuf Agha, which was identified either as a eunuch of the imperial palace in Istanbul (Van Berchem) or suggested to be identified as the Governor of Jerusalem (Natsheh). The function is unknown but most probably it was built as a commemorative dome for the good deeds of its founder.
The dome of Qubbat Yusuf, a semi-enclosed rectangular structure, is supported by three pointed open arches and a solid stone wall. Its exterior is covered with lead sheeting, and its interior is decorated with a ribbed pattern. Stone carvings and a marble-faced blind-niche decorate the northern face of the southern wall. Its lower half displays an Ayyubid inscription plaque, which mislead some researches to believe that Qubbat Yusuf was built during the Ayyubid period. An inscription that commemorates Salah al-Din's construction of a wall and a bridge over the ditch in 1191 shows otherwise.
Sources:
Natsheh, Yusuf. 2000. "Architectural Survey". In Ottoman Jerusalem: The Living City 1517-1917. (Sylvia Auld and Robert Hillenbrand, eds.) London: Altajir World of Islam Trust II, 936-9.
Gautier-van Berchem, Marguerite and Ory, Solange. 1982. Muslim Jerusalem. Geneve: Fondation Max Van Berchem, 63.
Burgoyne, Michael H. 1976. "A Chronological Index to the Muslim Monuments of Jerusalem." In The Architecture of Islamic Jerusalem. Jerusalem: The British School of Archaeology in Jerusalem.