Behind the door is: not a lecture hall.

It looks kind of like the fancy box seat areas in a sports stadium, if she's seen those, which she probably hasn't outside movies.

But she probably isn't paying attention to that anyway, because the facing wall is a huge picture window looking out on a galaxy, at maybe a sixty-degree angle to the galactic plane.

Her first thought is that this is the fanciest A/V setup she's ever seen and that they picked a great image to show it off. Then she realizes that the room being this big makes no sense with the building layout and walks in, staring around at everything.

It's laid out like a skybox, complete with seats; there are three loose rows all looking out toward the galaxy. Fancy seats, looks like leather.

The side walls are some dark wood, and go well beyond the wall she walked in through. One wall has a row of three minifridges under a long wood table matching the walls, and there's a sink and row of glasses.

The window has no internal frames breaking it up and looks flat, not convex. There's a thin railing a few inches away that keeps you from walking into it by accident, but it doesn't block access.

No other doors are visible.

Woaaaaah, TARDIS room, wicked. She pulls out her phone and snaps a bunch of pictures because she's absolutely going to doubt her own memory of this later. Then she opens the mini fridges and tries to turn on the sink, mostly just to convince her brain that this isn't a videogame environment and can be interacted with.

The sink has water, in multiple heats. Two minifridges have booze, the third has snacks - cheeses, fruits, and crackers, all prepared like for a fancy party or a catered corporate luxury box. (She doesn't see any meat.)

The door slowly swings shut behind her, which she may or may not notice.

She does notice, after it's already shut, and has read enough stories that even though she is not anywhere close to done exploring this place she immediately goes and checks whether she can open it again.

She can! It even opens to the same place it opened before. The door is entirely well-behaved. (Other than the part where it opens from a hotel corridor in New York to a skybox looking out over a galaxy.)

Okay, cool, not lost in the infinite multiverse or trapped in the faerie realm or whatever. She lets it shut again.

"Hello?" she calls. "Is anyone in here?"

There is no answer. There's also nowhere a human could plausibly be hiding, but that probably wasn't what she was expecting anyway.

Whatever caused there to be minfridges with recognizable food and booze must have encountered human minifridges and food and booze at some point and be the kind of entity capable of imitating observed phenomena, but that's about as far as she can speculate with any confidence. 

She goes up and stares at the galaxy window and tries to identify the galaxy depicted and whether it's a true-color or false-color image.

It's a true color image of a six-armed spiral galaxy, so definitely not the Milky Way. It doesn't match Andromeda either. She can't immediately identify it, so it's probably not one she's seen before?

Does Google images have anything like it? Assuming her phone even has signal in here; she might need to stick it out the door into a spacetime that's definitely contiguous with a cell tower.

She does not have signal while the door is closed, but it can connect if she leans on the door. This isn't too helpful, though; Google image search mostly just gives her artist's depictions of the Milky Way.

If she keeps the door open for a while, some of the other people headed for the tumor growth presentation will probably come in.

Good; maybe one of them will know what the fuck! She feels bad for the presenter, though; this is a hard act to follow and there's no projector setup. She holds the door for the first batch of biologists and wonders if any of them will be brave enough to eat the mysterious fridge food.

She may notice, while trying to look up images, that the official start time of the presentation passed while she was poking around. There is not a crowd gathered in the hallway like you might expect if the door to the room was blocked.

There are, however, people showing up slightly late. The first one narrows his eyes and looks at his phone while walking further down the hall (probably he assumed this was the wrong room). The next two, however, (a grad student and his advisor) actually look through the doorway.

The guy blinks at the galaxy, and the fancy seats, "That does not look like the room that was here this morning. What the hell?"

The older woman is a little slower to react but nods in agreement with that last part.

"I have no clue! It was like this when I got here and it's bigger on the inside and for all I know it's vacuum on the other side of that glass, though that seems kind of unlikely even given how unlikely the rest of this is."

"That's..." He trails off. Apparently he can't decide what that is. Eventually he goes in and knocks on the window, which doesn't make much noise.

His advisor looks kind of shell-shocked for a bit. Eventually she asks Brenda, "When did you, find, this? Just now?"

"A few minutes ago? I'd suggest asking the people who run the hotel what even, but honestly I'd be more surprised if they knew than if they didn't. I'm thinking maybe I should camp here until whoever did it shows up, and also put out some emails to all the physics people I know and get them in here with instruments. . . . Ideally starting with a Geiger counter. Based on the gravity we're still on Earth, at least."

"I probably know someone... maybe not a physicist but at least a radiology researcher. Let me check."

The other guy is examining the minifridges.

"This is exactly like fancy corporate box seats, but instead of football it's a galaxy. Someone has a weird sense of humor."

Then he notices no one's mentioned names. "Uh, I'm James Marston. That's Professor Kissenten, she's my advisor."

Professor Kissenten distractedly says, "Call me Shirley and don't make the joke," before going back to searching her email contact list for @nyu.edu names she remembers.

Brenda knew a physics major who graduated a couple years ago and got a job in aerospace somewhere in the city; she digs him up on the alumni directory and sends a "Hey remember me, come see this". 

"Should someone be getting the New York Times or should we wait for the physicists? I'm not sure I'd have anything helpful to say to a reporter if we had one. Oh, and we should check if time is doing anything funny, can you start your stopwatch at the same time as mine and I'll go outside and shut the door for a minute?"

James gets out his phone and gets his clock app in stopwatch mode. "Ready when you are."

Shirley has also sent an email. "I imagine the reporters would think it was a prank. Honestly, it still feels like a prank to me."

"I'm just glad you can see it too, honestly; I was about to start wondering if I had lost my marbles and the jar they came in."

To James: "On start, three, two, one, start." And once they've both started she goes out the door, waits ten seconds while watching the inside for signs of time shit, shuts the door for another ten seconds, then opens it again and goes back in to compare times.

Time seems to have progressed completely normally during the test. James's stopwatch matches Brenda's to within the centiseconds margin of not-quite-simultaneous button-pressing.

"Okay, so spatial but not temporal nonsense. Which is good, I guess? Oh, hey, does anyone think I should not try to disassemble the sink and see where the pipes go. I would also support a party going to the hotel staff and asking for permission to put a hole in the wall of the next room over but I think someone with more clout than me should do it." There, that's a polite enough form of chickening out of talking to an authority figure.

Shirley blanches slightly. "I'm not sure I have enough clout for that either. Maybe a conference organizer... Someone from the organizers is usually in the talk, to coordinate. We can check the next room over, except... where are the people who should be in this talk?"