This map, published by the Columbia University, shows the maximum extent of the Mongol Empire in the mid-13th century. The map shows the advances made under Genghis Khan in red and those made by his successors in blue.
It is important to note that the borders were never firmly established, so the measurement is usually taken as all the territories that were subjugated at that time, covering an area of some 24 million square kilometres. If we also take into account uninhabited territories such as the Siberian tundra, the Mongol Empire could be considered to have covered up to 33 million square kilometres. Taking either of these two references, the Mongol Empire would be the second largest in history.
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