The mau­soleum of Oljay­tu was con­struct­ed in 1302-12 in the city of Soltaniyeh, the cap­i­tal of the Ilkhanid dynasty, which was found­ed by the Mon­gols. Sit­u­at­ed in the province of Zan­jan, Soltaniyeh is one of the out­stand­ing exam­ples of the achieve­ments of Per­sian archi­tec­ture and a key mon­u­ment in the devel­op­ment of its Islam­ic archi­tec­ture. The octag­o­nal build­ing is crowned with a 50 m tall dome cov­ered in turquoise-blue faience and sur­round­ed by eight slen­der minarets. It is the ear­li­est exist­ing exam­ple of the dou­ble-shelled dome in Iran. The mausoleum’s inte­ri­or dec­o­ra­tion is also out­stand­ing and schol­ars such as A.U. Pope have described the build­ing as ‘antic­i­pat­ing the Taj Mahal’.