The Trabia Grand Castle is a castle located in the middle of the Imperial Reserve at Cyrodiil in the alternate Nirn called Axios, a realm of Oblivion created by a mysterious & very powerful individual. The city of Trabia itself is located within the castle's outer walls.
Located in the highest part of the castle, access to this area is heavily restricted, as it is where the Regent resides. It consists of a Conference Room at the lowest, an Oculory Room at the middle, and the Throne Room at the highest level. The throne is mechanically operated and can ascend or descend as the Regent sees fit.
It also houses the best airship hangars of Trabia along with it's powerful Leviathan-Class airships and frigates.
A staircase near the elevator room to the right leads to the private Hanging Gardens Suite, which also acts as an observation point with a telescope.
The middle level of the castle houses the dormitory of the highest court members of Trabia. Each court member has their own private suite, which is the equivalent of an 5-star room with complete essentials. It also houses the medical wards and the castle's large courtyard along with a pool area, which served as a place for Alteration (Waterbreathing), endurance, and athletics training.
The base level serves as the entrance to a massive labyrinth of tunnel networks that leads to every other city in Cyrodiil. It is currently sealed off at present, as a dangerous concentration of a deadly miasma-like mist made the tunnels into a no-man's land.
In addition to the seemingly infinite undead monsters that reside there, many traps also claim the lives of many trespassers. Many more fall victim to the tunnel's denizens and advanced automaton security systems.
This area was originally built for special occasions concerning couples. It is accessible through the Upper Level and is considered a restricted area for all except the highest court members. It also houses an dwemer-made telescope that allows a complete view of the Imperial Province.
- It is never mentioned as to why the Underground Levels were abandoned, but some speculate that an secretive underground organization uses the abandoned area of the castle as a secret inaccessible base.