The distinctive mountains in Venezuela are called Tepuis. What makes them so special?

Explanation

Tepuis are table-top mountains (mesas) that can only be found in the Guiana Highlands, especially in Venezuela. These geological formations often play hosts to a unique collection of endemic plants and aninmals. Some of the most special tepuis are Autana, Pico da Neblina, Auyantepui and Roraima. Auyantepui is the source of Angel Falls, the world's tallest waterfall.