Hidden Realm

The Hidden Realm was the divine realm of Annam All-Father, the chief deity of the giant pantheon. In the Great Wheel cosmology, it was located somewhere in the Outlands.

Geography
The exact location of the Hidden Realm within the Outlands was unknown. No maps existed with any information on the realm's whereabouts. It was speculated that the realm was magically cloaked from detection or located in a demiplane connected to the Outlands via a portal.

The realm itself contained a large crystal tower atop an enormous mountain. From the tower, Annam observed the workings of the multiverse.

Rumors & Legends
It was speculated by some sages that the Hidden Realm, in fact, did not exist. Others argued that the realm itself was the master control of the planes.