I was messing around with the new /place command and decided to spawn a nether fortress. (Or I guess since I was in the overworld, an overworld fortress?) I found something that was extremely weird. A random lavafall (lava waterfall) had generated below the fortress, with a nether brick below it.

This is probably very hard if not impossible to reproduce, due to it being completely random world generation.

Unfortunately, the picture of the outside of the lavafall couldn't be sent, so here is the inside.