The Firmamentum Saeculorum is located on the planet Erebusa in Void Space. There is no known origin of the structure, symbols related to several proto-european cultures are intermixed together including gaelic, germanic, french, and slavic symbols. The structure itself is located at the center of a large swath of grasslands which boarders a forested region. There is a large freshwater lake nearby and a river which travels to the East.
Composition
The structure is constructed from interlocking marble bricks so precisely cut and set that there is no mortar or other substance required to seal the bricks together. The marble itself is nearly perfect in its composition.
Exterior
The exterior despite being constructed with such perfect marble is aged and weathered, though it is unsure how much time has passed the structure has obviously been here for a very long time. It is built as a medieval style castle in much the same style and design as something one might find on ancient Earth during the dark ages. The structure is extensive, constructed jutting out from the landscape, a large bridge leads to a set of large double doors on the side while the main archway is toward the front with a large tower directly in front of it - a bridge connects the two. There are smaller entrances at the bottom of the bridge as well, which all lead eventually to the main foyer. The outside walls of the structure are solid and several feet thick.
Attempts to climb the exterior and enter a window from the outside will result in the person being pushed out of a window at the opposite side of the structure. Attempts to gain access to the interior through explosive or other similar means (portals, explosives, cutting torches, beaming) will result in the person being deposited in the foyer and all doors from there being locked, except from the exit.
Directly inside the main gate are two large double doors made of the same material as the exterior. The doors will open for anyone who attempts to push them open. Just above the main doors in embossed marble letters coated in white gold (a platinum / gold alloy) it says Firmamentum Saeculorum which literally translates to "Vault of Ages".
About a quarter of a mile to the north of the structure is a set of standing stones marked with runes. It will lead a person into the Verum Transitus. In front of the building is a Hermod Gate with no dialing device, it requires direct access from a Vertex Scanner, Tricorder, or similar portable computer with a transceiver.
Interior
There is a large foyer just inside the only doors, the large space has several tables with marble benches and some kind of ever-burning flames for light. These flames seem to be ignited as fueled from an unknown energy source, but they light any time a sentient being enters the structure. Around the outside of the foyer are doors, each one leads to a hallway of impossible length. Each hallway seems to go on infinitely and well beyond the boundaries of the structure's exterior.
Access
The vaults can be accessed from any plane of existence with the proper training, even if a person is not a magic user or psionic. There are a variety of methods, the owner of a vault usually must set or learn a method - though this method is completely a mystery - and then teach others. Some vaults are accessed via some kind of magically imbued key, others can be accessed through a psionic or magical spell. Another common method is transition through some other surface or structure - such as an enchanted door frame or gate or moving through a mirror or mirrored surface directly for the foyer. At the center of the foyer is also a Airgid Drochaid which allows access from Elder Soteria, though having a key is exceedingly rare and while some people have heard of this place, it is thought to be nothing more than a myth of treasure or ancient legend from before the Peace of Ages.
Obtaining a Vault
The method for obtaining a vault is completely unknown. There are a number of detailed writings composed of various proto-european, proto-asian, and proto-mediterranean cultures along the walls in the foyer. The mix of symbols and time periods makes translation nearly impossible as there is no key or rosetta stone anywhere in the structure. It is likely that these writings tell of the origin, history, and perhaps even instructions on how to properly use the structure and its vaults.
Rooms
Down each hallway are doors at regular intervals, the doors are all locked except to a person whom has been specifically allowed access to that door by someone else who has access. The mechanism for authentication is completely unknown but is 100% accurate. The doors lead to a storage room that also seems to go on forever and is impossibly large. The rooms are lined with windows that paradoxically will outlook over any number of the windows along the exterior, but never the same one twice.
The rooms cannot be broken into by any known means.
The room's appearance is suited to those who use it and shelves of needed sizes and of what the owner expects them to be built of will appear as needed. Reconstructions and expansions happen after the room is empty, there will always be enough space, though the filing system is entirely up to the owner the Vault itself will organize materials placed there according to whatever system is put in place once that system is established.