The world's largest lake that's 4 times larger than the runner-up - and not even a 'lake'

The world is home to some incredibly large bodies of water that cross country boundaries and stretch so far into the distance that they could go on forever.

The Caspian Sea in Central Asia, however, is by far the largest lake worldwide at a staggering 386,000 square kilometres, or 149,053 square miles.

This area is approximately equal to that of Japan and accounts for up to 44% of the world's lake waters.

It is so vast that it is four times larger than its closest competitor, Lake Superior, on the border between Canada and the US, coming in at a measly 82,000 square kilometres (31,660 square miles) by comparison.

Despite its name, the Caspian Sea is technically a lake as it is an inland body of water and not directly connected to an ocean. That being said, its salt content is similar to seawater's, stirring some debate on its classification.

About 14 million years ago, the sea basin of the Caspian was actually connected to the Black Sea, but tectonic shifts separated it, making it the landlocked body of water it is today.

It is known as an endorheic basin - one that doesn’t drain into a larger body of water like a river or ocean and instead evaporates or seeps into the ground.

The Caspian Sea is so vast that it is bordered by five countries - Kazakhstan and Russia to the north, Turkmenistan to the east, Azerbaijan to the west and Iran to the south.

Its salinity is approximately 1.2%, about a third of that of average seawater. The seabed in the south of the lake reaches an impressive 1,023 metres below sea level, making it the third-lowest natural non-oceanic depression on Earth after the Baikal and Tanganyika lakes.

Over 130 rivers provide inflow to the Caspian, the Volga River - the longest river in Europe - being the largest.

The lake also has several small islands, primarily in the north, including the Tyuleniy Archipelago, which are desert-like with little grass.

Baku, the capital of Azerbaijan, is the largest city by the Caspian Sea, with others also including Astara in Iran, Atyrau in Kazakhstan and Derbent in Russia.

About 850 animal and more than 500 plant species live in the Caspian, many of which are endemic. Six critically endangered species of sturgeon live in its waters, as well as the unique Caspian seal and beluga.