About 1055, the Seljuk Turks took over the region. In the 12th century, the city of Nakhchivan became the capital of the state of Atabegs of Azerbaijan, also known as Ildegizid state, which included most of Iranian Azerbaijan and a significant part of the South Caucasus. The magnificent 12th-century mausoleum of Momine Khatun, the wife of Ildegizid ruler, Great Atabeg Jahan Pehlevan, is the main attraction of modern Nakhchivan. At its heyday, the Ildegizid authority in Nakhchivan and some other areas of South Caucasus was contested by Georgia. The Armeno-Georgian princely house of Zacharids frequently raided the region when the Atabeg state was in decline in the early years of the 13th century. It was then plundered by invading Mongols in 1220 and Khwarezmians in 1225 and became part of Mongol Empire in 1236 when the Caucasus was invaded by Chormaqan. In the 13th century during the reign of the Mongol horde ruler Güyük Khan Christians were allowed to build churches in the strongly Muslim town of Nakhchivan, however the conversion to Islam of Gazan khan brought about a reversal of this favor. The 14th century saw the rise of Armenian Catholicism in Nakhchivan, though by the 15th century the territory became part of the states of Kara Koyunlu and Ak Koyunlu.