Azarbaijan, a province in the northwest of the country, is geographically varied with mountain ranges, fertile planes, and the large salt lake of Orumieh. Tabriz, the largest city in the region, was the Mongol capital in the 13th century and again under the Black Sheep Dynasty in the 15th century. The city is known for its (much damaged) Blue Mosque, and the covered bazaar which preserves the flavour of old Tabriz and where some of the finest jewellery and carpets in Iran are to be found. Another site worth seeing is the Sha-Goli Pavilion which is built in the middle of an artificial lake. Maraghe, ninety miles to the south of Tabriz is the location of an observatory built by the Mongol Hulagu Khan, grandson of Gengiz Khan, and several pre-Mongol tomb towers. The sacred ruins of Takht-e-Soleiman, a UNESCO World Heritage Site, lie in a broad and remote mountain valley by a lake to the southwest of Maraghe. The massive stone walls and remnants of 38 towers date from the 3rd century A.D were built by the Sassanids. Ardebil, is 130 miles to the east of Tabriz and its known for the magnificent tomb of Sheikh Safi-eddin Ardebili, a widely revered 14th century sufi philosopher. Shah Ismail, founder of the Safavid Dynasty, was sixth in decent from Sheikh Safi-eddin, from whom the Safavids derived their name. The church of Saint Thaddeus, also known as the Black Church, is located 13 miles from Maku. It is one of the oldest churches in Christendom, and holds special importance for Iran’s Armenian minority. At Soltanieh, 25 miles southeast of Zanjan, is to be found the tomb of Sultan Mohammad Khodabandeh (Oljeitu) – another UNESCO World Heritage Site and one of the finest achievements of Persian architecture.