These caves in the Amazon have never been seen before

This video is the first look inside one of the world's largest cave systems. It extends almost 13 miles under the mountains in the Amazon basin in Venezuela.

It's a vast and unique maze of caves that basically dwarf the explorers that are photographed inside.

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Not just anyone is allowed inside this fascinating geological phenomenon. The area is cut off by steep cliffs which means only expert cavers can navigate their way down there.

One of the Italian explorers able to get inside describes the caves as "a completely different world".Some of the things they were able to see inside include incredible stalagmites and stalactites.

The cave walls are also pretty unusual, having taken on a pink hue and the underground rivers have left a unique imprint on the rocks.

Quartz in the walls gives off a pink colour, while acids found in the water have the ability to turn the rivers red.

The expedition into the cave was led by Francesco Sauro of the University of Bologna in Italy.

Francesco and his team spent 40 days exploring the area, including the Imawarì Yeuta in Venezuela, which runs with at least 22km of tunnels, the New Scientist reports.

Jo de Waele is a geographer and cartographer that was part of the team and also comes from the University of Bologna.

Jo explained that they have no idea how old the caves are because there is nothing inside they can use to date the area.