I don't know about most, but generally those "background sound" sort of ambient things are pretty relaxing.
goes looking on YouTube for some examples
Rain: https://www.youtube.com/watch?v=8plwv25NYRo
Lake waves: https://www.youtube.com/watch?v=Se5NjX-cM5I
Ocean waves: https://www.youtube.com/watch?v=WHPEKLQID4U
I think that the shakuhachi, a Japanese bamboo flute, is relaxing to listen to.
finds an example on YouTube: https://www.youtube.com/watch?v=miUKO5g0ONk
checks
That being said, I don't know if it is internally divided.
There's a really large cave in Southeast Asia somewhere.
kagis
The Sơn Đoòng cave in Vietnam:
So that'd be nearly triple the volume of the Everett Factory. Though the cave has two holes in its roof, and I don't know exactly how you define "room" here.
https://www.youtube.com/watch?v=tOH4gbW18Ts
https://www.youtube.com/watch?v=xVpk7LQML8g