Half of Colma seems to be graveyards, but I bet they could fill it to the brim with 4 story housing units and not put a dent on bay area demand... always boggled my mind.
Sure, maybe a bunch of cemetaries ain't the most efficient use of space, but it's certainly a really cool use of space. I live in close proximity to it, and appreciate it as part of the not-quite-green-belt between Daly City and South San Francisco.
And for those that like videos, that link includes a Tom Scott YouTube video as well.