Procedural cave challenge

I’ve been messing around trying to see what ways I can bend noise to do my bidding. Trying to make caves which would be interesting to explore is a lot of fun.
It would be cool to see what other people can come up with! Its hard to get a good mix of unique features working together on different scales.

This one has 18 layers of noise stacked and hacked together in various ways. White is walls, black is open areas. I have been building this with a floor-plan view in mind, although it looks like it could work as a side on view if you had a jet pack.

(full image 3000x3000, 380kb): https://www.dropbox.com/s/hqka9d2ykg1na0m/NoiseCaveBig.png?dl=0