Here is a neat bit of ancient technology: A qanat.

A common problem in arid regions is how to get enough water for your irrigation needs. Digging wells is one possibility, of course, but the water table might be far beneath the surface.

However, the neat thing about the water table is that it runs parallel to the surface - so if the terrain rises up and forms a mountain, the water table will rise up beneath the mountain as well. Thus, you can tap the water within the mountain simply by digging a tunnel into the flank of the mountain.

Which isn’t exactly a trivial undertaking, of course. Still, some qanats in the Middle East have been in use for several thousands of years.

And for #TTRPG , such qanats represent a good entrance to the “Underdark”, or whatever the local “Realms Below” are called - or vice versa, and monsters might emerge from them. And what happens if a qanat suddenly ceases to bring water? Naturally, some daring adventurers have to go in there and solve the problem, or else an entire community might starve!

Potala Palace in Tibet

The Sumela monastery in Turkey’s black sea province of Trabzon

Mount Thor in Canada, featuring Earth’s greatest vertical drop of 1,200 m (4,100 ft), with the cliff overhanging at an average angle of 105 degrees (15 degrees from vertical)

Another candidate: The Centralia Mine Fire, an underground coal seam fire that has been going for sixty years, and which could continue to burn for 250 further years!

I wonder how dwarves or other subterranean civilizations would deal with something like this?

The Plain of Jars. Thousands of giant stone jars on a plateau in Laos. Many contain bodies. No one is entirely sure who built them or why.

Another one: The “Bergpark Wilhelmshöhe” in Kassel, Germany.

This is a masterpiece of Baroque landscape architecture, and the Hessian landgrave at the time was only able to afford it because his father sold of Hessian subjects to the British so that they could put a stop to those pesky rebels in the North American colonies. The park is built across a hill slope (and covers an elevation change of more than 250 meters). Its highlights are the “Wasserspiele” (“Water Plays”). On every Sunday and Wednesday during the warmer seasons, water is released from a vast cistern at the top, located beneath a giant bronze statue of Hercules. Over the course of 75 minutes, this water flows down a series of artificial waterfalls and channels until it powers a giant fountain close to the bottom of the park.

Beyond that, the park has all sorts of other attractions - a fake ruined castle, a fake ruined Roman aqueduct, and a series of miniature temples to assorted Roman gods. This park makes a perfect setting for all sorts of cinematic adventures and/or occult weirdness!

I have only ever seen Antarctica in a single game. The Thing. And I’ve played a bunch of Chthulhu games, so that’s wild (At the Mountains of Madness takes place in Antarctica and many of the games take snippets from that story and put them in their game).

Pamukkale in Turkey.

It’s a really cool hot springs area where the minerals are super saturated in the water and so deposit out in calcium carbonate. Over time it becomes travertine. But just the location itself looks super interesting.

In a similar vein, the salt flats in Utah. When there’s been a rain and there’s standing water over the flats, it becomes a huge reflection - absolutely fantastic set piece for both some unique RP or for a really interesting battle.

I don’t know if his is missing the spirit of the question, but i’d say many planets and moons in our solar system could provide inspiration, like the moon europa with it’s endless ice plain (the surface is amongst the smoothest in the solar system) and gigantic sub surface ocean. In a fantasy world their might be a civilisation down their. Maybe the ice sheet is so thick they never knew about the surface and are only learning about it now, because some recent event has exposed a part of their ocean to the surface.

Locations on earth? The mountain villages around the Himalayas in Napal. You walk endless narrow paths, cross forests, glacial lakes. The view is breath taking. The mountains grow into the sky like paintings. The air is as clear as it can be. You walk trough clouds and sunshine alike and all around you is nothing but wonder. And all along the way, in a place that is always hard on you and sometimes even hostile, there are little signs of the deep devotion the people of this place have for it. Sometimes it’s a little shrine, just a few stones staked upon each other. Sometimes it’s a little stupa. This places have been here for hundrets, some for thousands of years, maintained by generations of villagers. Their religion has the coating of Buddism, but it’s so much older. For in their religious practice they still call to the spirits of the land, yes, of the mountain itself. And it shows. This landscape, hostile as it may be to the casual traveler, has become something the locals not only tolerate, but actively worship. And there is a certain magic to that, a magic that has formed over thousands of years of love and worship. It shows in how every little shire, every stack of stones, is still maintained. It shown in offerings being made to the mountain itself at some shrines, every morning before the sun rises by a different family from the nearest village, every day since their people have come here in times untold. It shows in how the locals know the land by hearts, every path, every slippery slope, every treacherous segment of cliffs they traverse every day. In isolated places you can encounter the wise men of this people, whom live the lives of hermits. In a fantasy setting there would be druids, for they are as close to the real live equialent as i have ever met.