The correct answer to this open question is the following.
The location of Kiev contributed to its rise as the center of early Russia due to its geographical location and for being in the middle of a trade route Scandinavian people used to trade from Constantinople, the capital of the Byzantine Empire. Rurik, a Danish man, was the first king of Russia in 855, and establish Kiev as the most important city in Russia. The importance of Kiev ended in the 12th century, due mainly to the invasion of the Mongols.