Eden is the unofficial name of the large, empty space beneath the mountain range on the Mainland. It consists of a large, open cave of varying ceiling height. The ground is made of grass, completely flat except for a small area of water and sand--the source of the outside river. The only way into Eden is via a small hole in the map, located in the mountains near The Secret Cave.
Unlike any other cave in the game, the ground of Eden is made of grass. This is likely because the creator, Shagabash, did not make the mountain range on the Mainland solid, but rather hollow, and therefore there was no need to add a stone floor, as it was assumed that nobody would ever enter it. The only noticeable terrain feature of the cave, aside from the grass, is that the mouth of the river outside begins in here, as seen by the sand and shallow water near the entrance.
Being a cave, it is naturally quite dark. This presents somewhat of a problem, however, as Eden spans the entire length of the mountain range. If one looks off to one of the sides, fog is generated as the cave is too long to view in its entirety. Its height is less consistent, however. Due to being under varying mountain ranges, Eden is essentially a massive stone pillow fort. At the tallest point, Eden has a fairly high ceiling. At the lowest point, it is only four studs tall, too small for players to fit. Sometimes, the stone walls are replaced with brown pebble (dirt) walls, marking where the mountain above transitions into grassy hillside.
As Eden is one of the most inaccessible areas of the map, open to only a tiny area in a specific place, it is objectively the best place for tribes to settle safely. The entrance is easily defended, and it is difficult to leave Eden without dying, as the entrance is over fifty studs in the air. As well, Eden contains no resources of its own aside from sand. Due to this, any players attempting to settle here must bring any kind of food, tools, and structures that they want to use into Eden. However, if a tribe does decide to settle here, they may rest easy knowing they are completely safe from raiders. Bringing fruit trees guarantees an unlimited supply of wood and torches, and the sand near the entrance allows for sandstone wells and huts, but any stone structures must be brought in from outdoors.