Hey all. My group is getting close to entering a part of the adventure where the normal rules are suspended and I need some help with ideas. They are about to enter a place of high magic, where the rooms can be wildly different. What I would like from those of you who choose to help, are rooms that are fantastic in some way.
The rooms can include terrain (which would appear to be outdoors except for the walls) from arctic to desert, even from one room to the next, or just be a standard room. They can be highly dangerous as the group is high level to harmless. They can be beautiful or ugly. Have fun with traps and monsters from any edition as I will convert them. Also, feel free to create conditions or effects that aren't included in the game and I will come up with mechanics for them. Don't hesitate to give me your ideas on mechanics.
The room sizes should be vague as I will set the actual sizes. Tiny, small, medium, large, very large, gigantic, etc.
You can give me a very small description if you like and I will fill in the details, or if you want to do a detailed description, I won't be upset 
Some examples.
A meadow room with rainbow butterflies that leave rainbow dust trails behind them as they fly. No other effect.
A room with a crevasse running through the middle hidden by illusion and that has a strong downward gravity pull when you jump over it.
A desert room with a pyramid in the center. A pharaoh's ghost inhabits the pyramid and approaches any who enter the room.
Thanks in advance!
A cylindrical hamber of mirrored walls (taller than it is wide) and a beholder zombie that floats high above. (Maybe more than one.) The way out (other than the way the PCs entered) is a hole in the ceiling from which dangle long chains that almost reach the floor. The mirrors have the effect of redirecting rays that miss their targets. Any time a PC succeeds at a saving throw against a beholder's ray attack, it bounces off a mirror and redirects toward another target in the chamber (determined randomly). If a ray misses a second time, it is absorbed into the mirrors and powers a trap in the floor - iron spikes thrust upward violently before retracting again and resetting.
A room that is a void with several floating platforms on it. Some of the platforms have doors on them, which open to other rooms just fine despite not being attached to any walls.
A room that is all pink and squishy. It shudders when someone steps on the fleshy floor, and squeals of pain can be heard if something hits the walls or floor too hard. Gibbering mouthers could possibly emerge from the walls.
In one adventure I was running a few months ago, I threw a room in (on the spur of the moment) that was kind of fantastic for where they were. They were exiting a typical dungeon room through a typical door, and stepped into very large forest with no obvious walls around it anywhere, except for a cliff behind them with the door they came through, which was now shut (and locked).
The first thing they saw was a beholder giving orders to a group of humans who had been turned into it's slaves. There was a dirt road in the middle of the forest with a horse drawn wagon just sitting there (I gave them a way to escape the beholder b/c they were too low level to fight it and win). They did take the wagon once the beholder spotted them, and it chased them for awhile, but they eventually got away.
I then had them pass a very mirror-like pond that had some shimmering items in the water. They took the hook and as they each reached in, I rolled on the PHB trinket table and they all got a really cool little momento of the room. They eventually found another cliff with a door in it, and after it was unlocked by the rogue, they were back in a normal room in the dungeon.
Interesting and good stuff!
A room where the PCs are fighting on a giant clockwork device. They are standing on the gears as the move around and getting from one "level" to another requires grabbing onto a gear and riding it up.
Hazards include having to get out of the way of meshing gears and avoiding the occasional pendulum. In addition, if this is an actual clock the chimes may be deafeningly loud.
Extra points if you print out some gears on graph paper and actually have them rotating.
There was a thread a while back about different things that illusion spells could directly and indirectly do, and one of them was that if you used the Minor Illusion spell to create an illusory torch, the light cast by the torch would also be an illusion, meaning whatever was "Illuminated" was actually one of three things. A). part of the illusion, if it was within the illusion's radius. B). An actual object being illuminated by the light produced by the illusory flame. or C). Is neither the illusion or real, but is instead something being filled in by the mind of the individual that believes the illusion. They know that the light is illuminating something, but can't see it, and as such, their brain is forcing them to see something just so everything can make sense.
If you decide to go with this idea, the most interesting thing I've come up with is placing illusory torches all down a hallway and seeing how quickly the PCs either lose their minds, or figure out how to get through the area, either way, it should result in entertaining situations. Only problem is, you have to do it in such a way that neither the players nor their characters realize what's happening until they figure it out, which could be difficult. If you're running a game where the players are okay with you rolling for them every so often, this could be a fun exorcise.
A sphere shaped room where gravity always pulls away from the center of the sphere. You could look up and see a desk on the "ceiling", yet be able to walk around the sphere and sit at that desk. If you throw an object past the middle of the sphere it is affected by the gravity on the other side and falls to the "ceiling". Maybe there could be Walls of Force preventing you from getting to a certain spot in the room and you have to figure out a way to jump through the middle of the sphere to get to the other side. Or there could be a puzzle that has something to do with liquid and the strangeness of how it would look to have liquid surrounding you on all sides due to the gravity of the room. Maybe have platforms around the center of the sphere that you can rotate around the center and they emit reversed gravity in a cylinder under them, making anything under the platform fall toward the center of the sphere rather than away from it.
One very tall room is an exercise in climbing UP a cliff (or rusty ladder if your group isn't very Athletic). But when you get out the door at the top, you are on the next level DOWN in the building.
One room's floor is composed of XL letters. The spaces in between the strokes drop away beyond the reach of your lights. You have to jump from letter to letter to spell out a code word. If you mis-spell it, the room scrambles itself (and shoves you back by the door) and you get a floor full of XL letters in a foreign script. If you keep messing up you eventually get an extinct language using an extinct script. For ease of use, go with an IRL word in English - then French or German - then Latin - then Cyrillic script (Russian?) - then Classical Greek - then Egyptian hieroglyphics. Inspired vaguely by Indiana Jones and the Last Crusade, "the Name of God" test.
One room holds random portals connecting the Planes of Earth, Air, Fire, and Water. You have to enter the doors in a certain sequence to get to the next room. Locations chosen will not immediately kill the PCs (no burnt, drowning, squished, poison gas). If / when the PCs get it right, they find some cool little thing in their supplies - like all their canteens are topped-off full of fresh water.
You are on an outdoor balcony high overlooking a prairie. You seem to just be floating in mid-air. Nothing happens here for a long enough time to take a Short Rest. You can walk back through the door at any time. If you try to take a long rest, some Large flying monster comes over and tries to carry you off to its nest ... full of hungry (and carnivorous) chicks.
This room has walls, floor, and ceiling made of water. You have to swim through the walls a short distance to get out.
This room has walls, floor, and ceiling made of bones. To get anywhere you must arcane-cast Animate Skeleton or cleric-cast Turn Undead. This organizes the bones and makes room for you to move.
Lots of good stuff guys. Thanks a bunch.
A beautiful wooden room with six well made beds, and warm sunlight pouring in through the windows. Hunting trophies and paintings are on the walls. A fresh roasted pig hangs above a fire, and rose petals cover the floor. The air is rich with the smell of roasted pig and flowers. At both ends of the room is a simple wooden door, like one might find in an expensive inn. At first this room seems like a perfect place to rest. Almost too perfect. But the beds are all mimics, and will try to devour the players if they take a rest. The room ahead leads to the next room, which of course is totally different again.
Anyone else have any ideas? I'm working hard on this on my end, but I have a lot of rooms to design. 
Given that PCs often never make it to 20th lvl, it might be interesting to enter a room with a mirror or reflective surface allows the PCs to view the future:
While in the room, they can see themselves in another place, at another time, in one of infinite possible futures, where they are 20th lvl and fighting a great threat. Have combat using the 20th lvl versions of their characters (you can make them or let the PCs- it's just one of infinite possible futures, so it's not like it's set in stone). Win, lose, or even have the magic fade before battle concludes, leaving them guessing.
This room is full of items just randomly placed all over the floor (camping equipment, loads op potions, probably a few scrolls, some non-magical backup weapons and armor, all of someones lifesavings in gold, and some food-items that have been forgotten about). Once in a while a hole in the celing will open (letting sunlight into the room), a hand will slide in and some item will magically float from the ground to the hand which then takes it out. Or the hand will deposite something in.
The wizard went to great length to make a literal backdoor into a bag of holding, only to find out most adventurers that the bag wound up in only use it to store crap. The wizard kept the door, in the hope that someday someone will place a nice artifect into the bag.
In the same vein as the previous post, the door leads into whatever the inside of a (Giant-sized) Bag of Devouring looks like. If the PCs are not careful to keep the door open until they find a way out, they might get trapped inside. For whim, somebody might stick a hand into the Bag and rummage around a bit.
A room with two mirrors and two doors. You have to be sucked into one mirror, walk "around the outside of the room", step out of the other mirror (Alice in Wonderland style) before you can leave via the other door. If you haven't been through the mirrors yet, walking out the far door leaves you in the hallway outside the first door.
Thanks guys! Definitely using ideas offered up here. The players are going to have a blast.
A long hallway that twists as it goes, where the floor becomes the wall, then the ceiling, then the other wall, and finally the floor again. However, the carpet down the center provides its own plane of gravity.
This is actually for a dream sequence I'm planning to run soon.
The hallway twists 360 degrees before reaching the end. From the perspective of the start point, if they stay on the red carpet, they go up the walls, onto the ceiling, and eventually back to 'right side up.' Along the way there are statues and paintings that try to knock them off the carpet.
The group can just move straight ahead, effectively progressing along the wall and toward the ceiling, but midway there's a gaping hole in the floor at this point (which is really the ceiling) that sucks everything into it, and deposits it back at the beginning. There's a series of windows that can be jumped through, causing you to appear through another window. All the while, there's a bunch of modron-like creatures steadily moving up the hallway, who self destruct when they reach a PC, damaging the carpet. It's possible to 'lose' this scenario if they destroy the carpet in the middle.
Use/modify as you see fit.
https://drive.google.com/file/d/0ByIKNlh9cuvcRHhlZU15OU9xWU0/view?usp=sharing
A room that looks like the Esher painting of stairsteps
On one wall is the famous "Scream" painting. On the opposite wall is a painting of ... whatever he is screaming about.
Ditto the "Mona Lisa" and whatever makes her smile.
Mosaics (or something that can be taken apart and re-assembled) of the major gods, each with something wrong about them. (Bane holding a bouquet of roses. A male god has Sune's long red hair.) Each portrait must be restored to an Orthodox representation. Test your group's lore.