I was looking at some photographs of caverns (Luray Caverns, Shenandoah Valley, VA in particular) and I always wondered by games, particularly 2D JRPGs, tried to create something more natural and pretty looking than repeated 16x16 brown tiles. I figured making these spires in top-down is pretty difficult to pull off, but it is well-worth the effort to making an overused dungeon setting more interesting. Every time I walk into a cavern area, I just groan because I already know what is going to come. At least some games make it painless, but ones with random encounters and endless hallways of these bastards? God bless the fast forward feature in emulator.
Source: 1, 2, 3