Kartli ( ) is a historical region in central-to-eastern Georgia traversed by the river Mtkvari (Kura), on which Georgia's capital, Tbilisi, is situated. Known to the Classical authors as Iberia, Kartli played a crucial role in the ethnic and political consolidation of the Georgians in the Middle Ages. Kartli had no strictly defined boundaries and they significantly fluctuated in the course of history. After the partition of the kingdom of Georgia in the 15th century, Kartli became a separate kingdom with its capital at Tbilisi. The historical lands of Kartli are currently divided among several administrative regions of Georgia.