Looking at these amazing pictures posted at Country Life, you can almost picture a super villain lounging around, petting his (evil, of course) cat.
This "Subterranean Mansion" in Bowdon, England, is entirely built underground and comes complete with a swimming pool with waterfalls and slide.
This ultimate super villain lair can be yours for only £2 million.
http://www.countrylife.co.uk/property/details/property/429380/referrer/search/for-sale/Bowdon-Cheshire.html - via gizmodo
From the Upcoming ueue, submitted by calebkraft.
I'd make the entrance a TARDIS replica. That'd be awesome.
It would be pretty energy efficient too with all that insulating dirt around you.
Natural lighting would be by light-pipes.