Stretching for a relatively small span of 60 kilometres, the Eastern Tepuis are also known as the Roraima–Ilú range. The characteristic flat-topped mountains run along the border of Guyana, Venezuela and a small part of Brazil. They are remnants of an ancient sandstone plateau reputed to be billions of years old that once covered an area of roughly 200,000 square miles in the heart of the Amazon. Over millions of years, erosion left 100 tepuis across the region, ranging from 1000 to 3000 feet high. The main summits of this chain of mountains are Roraima-tepui, Kukenán-tepui, Yuruaní-tepui, Wadakapiapué-tepui, Karaurín-tepui, Ilú-tepui, and Tramen-tepui.