Use of geyser/sauna

[KoV]

Use steam from geyser or fire+water
Electric sauna later

Increase rest social (if with others) and comfort on higher tier

Would need some sauna bench for the comfort part
A structure/furniture for on top of geyser
A structure that consumes water,wood and stone if not using geyser
A structure that consumes electricity + water

Sauna area generates heat
Closed of area with geyser in it (indoors) generates heat

Can use geiser this way to create heat in cold areas or winter
Ofc this will create trouble in a heatwave or summer so using a geiser would come with its pro's and cons

[Astasia]

They already generate heat. Build a wall around them with a roof and the room will heat up.

[KoV]

the rest of the suggestions then

[GuessMDK]

I like it. It could be a great rest and relaxation area that adds comfort and joy. The balance would be the price of constructing it, and you wouldnt be able to use the geyser for creating electricity. I think those trade offs would easily balance out a new joy/comfort room.