It is believed to be unaccesible/ unreachable area till now. Even from the interview made by TibiaWiki with Delany (the Lead Product Manager) the screenshot provided exclusively by himself presents board which says:
"Maintenance Area!
Only Gods & Celestials!
Mortals Keep out!"
and is signed "A place we mortals will never be."
It was recorded by Tibia Fandom that this place was accessed only once -by Aeldene Stonebridge (as a reward by Knightmare) somewhere in December 2006- however access was given only by teleporting there.
The pictures by Tibia Fandom present "small" exhibition of items as follows:
They are signs which each says different information
1. Club of the fool
2. All experience, robbed by bugmonster.
3. Cipreis Demonsbane
The items which can be find are:
- Flowers which look like God Flowers 
- Boots which look like Leather Boots 
- Legs which look like Chain Legs 
There is also one screenshot uploaded by "Temahk" without Characters name presenting one more sign
4. Codex of Ultimate Boredom
Under each item there are other items hard to identify.
With the Book (black) 
behind it.
"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."
Source- Tibia Wiki - Fabulous Items of Tibia
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