NASA/GSFC/Arizona State University) apparently shows a collapsed lava tube, but I think it looks cool (like an open mouth with the tongue at the bottom).
I remember decades ago going with frieneds to explore a lava tube somewhere in the desert outside Flagstaff. You'd think they would be fascinating, but in the absence of any prior human activity, they are really quite boring geologically. Or perhaps we picked a poor one.
This is one of about 30 photos in yet another magnificent assemblage at The Big Picture.