As the undisputed king of inland bodies of water, the Caspian Sea holds a unique status. With an area of 371,000 square kilometers, it is more than four times larger than Lake Superior (the largest freshwater lake by area), and its total volume even exceeds that of all the world's freshwater lakes combined. Interestingly, despite being called a 'sea,' it is technically a saline lake with salinity levels about one-third that of the ocean. The Caspian acts like a temperamental giant; its water levels have fluctuated wildly throughout geological history, and it is currently facing significant ecological threats due to shrinking water levels caused by climate change.