The Watcher's Sanctuary, also known as the Great Tree Pub, is a area located in the J'taeri District of Ae'gura. This location is completely enclosed, and while also based in the Cavern, was unreachable without Linking Books.
The most notable feature about it is the Great Tree, an immense tree built out of stone, which represents a concept from D'ni religion.
The Pub and Tree were built shortly after the arrival of the D'ni people in the Cavern, and it changed hands many times. One of its owners was the Watcher, a Nostradamus-like D'ni prophet. Shortly before the Fall of D'ni it became the property of Guildmaster Kadish.
Rolep is an older name for the place which it held during beta testing, and which is still used in the game files. The Watcher in his journal in the Path of the Shell mentions that Rolep is when he first began to receive his prophecies. It does not occur in Uru otherwise.