Castle Greyhawk
From Merric's Greyhawk wiki
Castle Greyhawk was once the home of the Mad Archmage and Mayor of Greyhawk, Zagyg Yragerne. It has many dungeons beneath it, and is a place where much wealth can still be found.
It is rumoured that detachments of Elves and Dwarves guard the way into the Castle, and exact a toll from all who enter - and leave.
A chasm of 30-60 feet deep runs around the Castle. Several caves inhabited by a range of humanoids and other monsters live there.
