Sima Humpboldt, Venezuala
Located on the Sarisarinama Tepui, a remote 3,500m tall flat-topped mountain holds two huge sinkholes which were only discovered in 1961.
The largest of them, Sima Humboldt, is so large that it has its own ecosystem at the bottom!
Early research on this ecosystem found a number of plant species that were new to science.
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