Honestly, the first thing I thought of when I saw this is the precipice of Minis Tirath, the white city in LOTR:o) Mount Roraima is located on the triple border point between Brazil, Guyana and Venezuela.
Grímsvötn is a volcano in South-East Iceland. It is in the highlands of Iceland at the northwestern side of the Vatnajökull ice-cap. The caldera is at at an elevation of m ft). Beneath the caldera is the magma chamber of the Grímsvötn volcano.