South America’s tepuis – ancient table-top mountains with sheer vertical cliffs rising over 1,000 meters from the Venezuelan and Brazilian rainforests. Formed from two-billion-year-old sandstone, these isolated plateaus feature flat summits spanning hundreds of square kilometers, carved by erosion into dramatic landscapes of pink rivers, sinkholes, and bizarre rock formations. Witness how their extreme elevation and isolation create distinct climatic zones, from tropical jungle at their base to

FIRST LOOK: Alex Honnold is on a new mission to climb to the top of the "island in the sky," known as Tepui in the new National Geographic show #TheLastTepui. https://gma.abc/2W2KUjg | Good Morning America