User blog comment:UnboundIsaac/Oh No!/@comment-26139174-20150427001419/@comment-3157150-20150427002833

I actually did this when I first started playing Terraria  (back in the days of ~1.0.6) , the whole thing was on top of a lava pool with an obsidian layer beneath it. Can't do that now, the damn insects will get to you! (If the plants don't get to you first...)