I've also seen information suggesting people's welfare is better with windows, too - particularly windows that look into nature. If you can't be in it, look at it!
To generalize (as I'm known to occasionally do) it seems like messy/unmessy things - like trees, rocks, water - which have very small rules governing their structure, but live and die by those rules, feel good to us.
I find the challenge for me is maintaining the delicate balance between structure and disorder in my own time - ritual and order for work, strange and unpredictable recreation[fn:1].
[fn:1] What a weird word.