Siirt Ulu Mosque, located in Siirt downtown, was first built by Seljuk Sultan Mahmut Muğizud in 1129. The construction was planned to form in rectangular and in east-west direction. Siirt Ulu Mosque has a space which is covered by three domes side by side sitting on an octagonal drum in the direction of Qibla and it consists of two perpendicular barrel-vaulted sections in the east and west parts of the domes and it has two transverse transepts in the north and a space cut with a perpendicular nave in the middle section. Siirt Ulu Mosque undergone structural changes from the period it was built (1229) to 1985 so it is in question to have some changes between the present situation and the original version of the structure. As the body of the minaret of Siirt Ulu Mosque is segmented into a variety of decorations belts and in terms of upwardly narrowing, it resembles Karahan, Great Seljuk and Atabek periods minarets. The upwardly narrowing and segmentation in Anatolian Seljuk minarets is less. The glazed bricks in minarets of Seljuk in Iran and Atabeks in northern Iraq are not so many as in Siirt Ulu Mosque minaret. The minaret of Siirt Ulu Mosque; in terms of the architectural and decorative features, it has a special place in Anatolian architecture. Free stone, rubble stone and bricks were used in the construction as a main material and brick-dust was used as binding material in tiles decoration. In the last century, the mosque has been surrounded with one or two-story concrete buildings, formed unlicensed and unqualified, and it has become almost unrecognizable from outside. With the conservation projects prepared by Bitlis by the Regional Directorate of Foundations in recent time, the majority restoration work was completed between the years 2008-2013. The expropriation work of private property is still continued and the southern and western perimeter wall repair is partially completed.