Biomes - environments that fall into a certain category - are a great way to set the atmosphere for a specific adventure. We all know of deserts, forests, swamps, mountains, and so forth, and each of these biomes have their own iconic adventures and adventure sites.
But the real world is full of obscure, unique environments that aren't known to many people - let alone #ttrpg players, which makes them a great option to bring variety to a game - and fantasy and science fiction has come up with all sorts of further biomes that aren't known on Earth. So what are your favorite obscure biomes?
Personally, I am fascinated by so-called "Cloud Forests" ever since I heard of the concept. They are usual tropical or subtropical forests which, due to their geographic locations, are shrouded in fogs for much of the year. In RPG settings, forests often hide many dangers due to their low visibility - and so does fog. It's two great tastes that go well together!
Howabout:
Currently, actively calving glacial field.
Cave system that is only fully traversable via fully immersed swimming. Throw in bioluminescence if you have some pity.
Any kind of environment where the flora are actually radiotrophes, but you don't know that yet.
Melting tundra prone to methane leaks/explosions/ghost fires inside of trees. No, I didn't fart, but we are all about to asphyxiate.
'Hole in the sky' environments where due to atmospheric degradation / large scale geomagnetic anomalies... you're either gonna need serious UV protection, or else everyone is getting really tired, very thirsty, and seriously sunburned, very very fast.
Also all the locals have so much cancer that it's a part of their religion/culture.
WW1 rainy mud wasteland... the entire area is basically quicksand.
Toxic salt flats.
Some kind of niche micro biome where the flora/fauna just actually rely on the evaporation/condensation cycle + regular vortexes to breed/propagate.
Like a species that has a lifecycle that begins and ends in the water, but the majority of it is spent on land.
They get to land by a bunch of fertilized eggs being fairly regularly hoovered up into the sky, which are then rained down on the surrounding area.
And finally:
That's not a bunch of pretty ponds, those are geothermal pools.