The exhibition of Fabulous Items of Tibia is one of the three wonders that can be found under the Plains of Havoc. Unfortunately, there is no possible way to enter the dungeon with all of these fabulous items, as the access hole in the Shrine of Wonders is blocked.
During the test server that implemented the Pits of Inferno quest, Aeldene Stonebridge was rewarded by Knightmare for solving big parts of the quest line. He teleported together with her to the inaccessible exhibition.
To the south of the area pictured below, are different rooms with switches for "lag", "kicks" and more. As far as anyone knows, no player has entered this room ever since.
Aeldene Stonebridge at the Fabulous Items of Tibia during a Test Server
Delany's Exclusive Screenshot for His Interview with TibiaWiki
The Codex of Ultimate Boredom is one of the Fabulous Items of Tibia