Soltanieh Dome lies south west of the Cohan Dej (Royal citadel) 43 km from Zanjan and was commissioned by one of the Ilkhanate kings (Oljaytu) in the year 1302–12.The dome of this construction weighs 200 tons and is situated on pillars, bearing an area of 50 Esq. This structure is made of a mixture of gypsum and to a lesser proportion limestone. The octagonal building is crowned with a 50 m tall dome covered in turquoise-blue faience and surrounded by eight slender minarets.
Soltanieh dome is erected in three floors which are defined as follows. The ground floor consists of the eight portions. The first floor comprises of the halls which run throughout this floor. On the third floor is the foundation column of the dome and the octagonal pillars supporting the 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’. The entrance to the cellar is from the southern portico. The layout or plan of this cellar is a complex one, consisting of 7 segregated sections, each part independent of the other. The monument is of high artistic value For Example a spectacular engraving that stands 360 cm high in which a verse from the Holy Quran (Sureh Fath) has been inscribed in the beautiful script of ‘Tholth’. On the upper or second floor of this structure engravings can also be observed, one of these inscribed with the (Ayeh 125 Sureh Baqareh) from the Holy Quran inscribed in the “Kufic” script. Soltanieh Dome is an important historical site and one of UNESCO‘s World Heritage Sites since 2005.