My daughter almost bought a house with a bunker a year ago, and lost it to a higher offer. Well, it used to be a bunker. Back in the 50’s, the neighbors on the block helped the then-homeowner build a large bomb shelter-type room under his home. When my daughter looked at it, it had changed hands several times, and the bunker had been converted to a very cool home theater, carpeted from head to toe, with a giant tv and those huge, comfortable theater chairs sprinkled about.
There was no claustophobia feeling whatsoever, the ceiling was quite high and the room was large. I’ll bet there are many homes from that era with those types of rooms.