"Twelve! Get going. You're risking an intersection!"
The grumpy old bleached gnome at the desk is pointing at a bowl of water next to him. It doesn't seem to be anything unusual but the young gnome lad's eyes go wide and he nods. Looking back he begins to ask for the key again but then sees that Kamea has been presenting it the whole time.
"Oh. Sorry. Right."
He snatches away the key, takes a quick look at it and then nods. He begins walking down the hallway towards the giant vault door at the far side of the room.
"As I said your curator will be able to answer your specific questions but I understand if things are a little bit disorienting. Presently you're in the Klacken Exchange, an interdimensional magical exchange, hence the name. Well I guess that isn't completely obvious. My name is Josianamus Klackencogswheel, hence the name. Originally it was the Klackencogswheel Extraplanar Magical Exchange but none of our clients seemed to like that very much so it was eventually just shortened to the Klacken Exchange."
He pauses, looking over his shoulder to make sure everyone is still following. By then the group passed by the desk with the old gnome who gives them a quick judgemental look before calling out to the young gnome,
"Vault Four," before going back to studying the ripples in the bowl of water. The young gnome nods and continues leading the group down the hallway.
"The key that you handed me is what we refer to as a guest pass. Our clients can get them issued to allow select guests access to our inventory. Sometimes it is just to do some shopping for the client but many times keys are given out as rewards for services conducted. Each key is single use however. Once your needs have been satisfied, within the limits of your client's tier of course, you'll be transported right back to the exact time and place that you came from. Here we go..."
The gnome stopped about fifty feet away from the giant brass door. The door itself was covered with small engravings depicting various magical scenes. Wizards casting fireballs at dragons or reading ancient tomes or performing grand rituals. The engravings were so detailed that as the party walked forward the way the light and shadows hit the engraving caused them to appear to move. The fireballs would explore, pages would be turned, rituals circles would appear to glow. At first it looked magical but it quickly became apparent it was just expert craftsmanship and tricks of the light as the scenes just flipped back and forth over and over again.
Number Twelve, aka Josianamus, was standing next to a lever set into the marble floor. The young gnome began pulling and pushing the lever, flipping it through a complex series of positions. The ground began to rumble but instead of the giant vault door opening instead the whole wall began to rotate. Along nearly invisible seams the vault door and the wall behind it rotated clockwise so the giant brass door sank into the floor like a setting sun. As it did so on the other side of the wall opposite a new vault door came into view like a sunrise. This one was engraved with pictures of kings and rulers commanding armies and demanding loyalty from their subjects.
This door rotated up into position like the sun rising to midday but then didn't stop, it too continuing to rotate over and set, disappearing beneath the floor. A third vault door rose up and this was engraved with what looked to be heroes fighting terrible monsters or avoiding deadly traps. This time when the vault door was fully visible it locked into position. The gnome pulled the lever one more time and this time the giant vault door opened.
Through the door was what looked to be a giant warehouse filled with shelves.
Looking like library stacks but instead of books each shelf was full of boxes of varying shapes and sizes, each with a little card on the front labeling it. While the shelves themselves seem organized the overall layout is more akin to a maze and very little of the room is actually visible through the haphazard shelf layouts.
Standing on the other side of the vault are two more gnomes waiting patiently. One has a badge that says "#4" and the other has a badge that says "#8". Looking at them it would appear that the gnomes must all be related. Between #4, #8, and #12 it could easily be grandfather, father, and son.
Number Twelve runs forward, handing the key off to Number Four before heading back to man the lever, presumably to close the vault once the party had entered.