Elemental Plane of Earth

From DMG: 
Earth symbolizes stability, rigidity, stern resolve, and tradition. The plane’s position opposite the Plane of Air in the ring of the Elemental Planes reflects its opposition to almost everything air represents.
The Plane of Earth is a chain of mountains rising higher than any mountain range in the Material Plane. It has no sun of its own, and no air surrounds the peaks of its highest mountains. Most visitors to the plane arrive by way of caves and caverns that honeycomb the mountains.