Read this: The craft has also been popular in early medieval Rus, inherited as part of the Byzantine tradition. Yaroslav, the Grand Prince of the Kievan Rus' built a large cathedral in his capital, Kiev. The model of the church was the Hagia Sophia in Constantinople, and it was also called Saint Sophia Cathedral. It was built mainly by Byzantine master craftsmen, sent by Constantine Monomachos, between 1037 and 1046. Naturally the more important surfaces in the interior were decorated with golden mosaics. In the dome we can see the traditional stern Pantokrator supported by angels. Between the 12 windows of the drum were apostles and the four evangelists on the pendentives. The apse is dominated by an orant Theotokos with a Deesis in three medallions above. Below is a Communion of the Apostles.

What was used as a model for the church Yaroslav commissioned?
What is the answer? (If it cannot be answered, return "unanswerable")
the Hagia Sophia