Somehow you’ve gotten your dream home. The cabin in the mountains, penthouse downtown, castle nestled deep in the woods, nuclear bunker in the hills, or whatever. Whats the bit you’d add that might raise a brow from others? The fireman’s pole? The slide? The moat? The hidden room behind a bookshelf where you keep your stuffed animals?
Oh. In that case, it’s probably because of foundation. A basement can’t just be dug up out of the ground, it needs to be built in a certain area where you could do that safely and efficiently. If it were possible, I’m certain the bomb shelter boom during the cold war would’ve birthed some second basement levels.
Not sure if this counts, but my best friends technically have one of these as well, they have a semi-homemade indoor pool in the basement and it’s just deep enough to contain a hidden door on the side of its interior, which makes it “below” the regular basement. I’m told it’s an emergency tunnel.