This historic structure, located in the center of Sivas, was built in 1564 by Koca Hasan Pasha, one of the viziers of Sultan Suleiman the Magnificent. It was restored in 1968 by the General Directorate of Foundations. It is also known among the local people as the Çukur Mosque.
The mosque is constructed of cut stone and has a rectangular floor plan. The roof is supported by four thick, square columns and is covered by a sloped roof. It features a minaret with a round brick shaft and a single balcony, standing on a square base. The mausoleum, where the famous Sufi mystic, scholar, and poet Şemseddin Sivasî and his relatives are buried, is located in the northwest corner of the mosque courtyard. Built with cut stone exterior walls, the mausoleum features an octagonal drum on the outside and is covered by a single dome.