Swamps. There's a good one in Baldur's Gate 3 that I would like to see expanded in some future game. Basically the swamp is just a wetland when you first show up but if you pass an investigation check it becomes a fetid swamp. There are some dangers like plants that cause you to bleed and then if you don't heal you get infected with a disease. Unfortunately it's just a small area but it'd be so fun as like a whole campaign I think. Maybe with a spore druid, gloomstalker, and necromancer.

@juergen_hubert
The chapparal, or similar semi-arid locations. You see lots of plains and lots of deserts, but rarely the scrublands in between.

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.

For land environments, I can't think of any that have been unused, but for aquatic adventures there are a few possibilities:

• Coral Reefs - a whole maze full of creatures
• Sargasso Sea - Vast mats of impassible plants containing wrecks, hidden islands, etc.
• Deep-sea vents - the closest thing we have to an alien environment on earth..

Where in the world is the photo from?

A few that have come up in my group are maritime chaparral, savannah, karst hills, and fog forest.

The fog forest was my favorite: we had a culture in the area that would burn the forest in the summer to encourage beneficial plants to grow the rest of the year. We called it "the smoky forest" and decided it was generally clouded in fog, smoke, or both depending on the season. In our description it resembled a coastal redwood forest.