What would be the best thing you could reasonably expect to find in a cave?

Best, or reasonably?

A sense of excitement and awe if you like to explore. great visuals and perhaps an undisturbed pool of clear water that has not been contaminated by bat dung and looks like a deep reflecting mirror.

If you are into materialism and its an unexplored cave, then perhaps a box full of treasures like gold and jewels someone had hidden would be best.

If you are into history the best thing would be undiscovered cave paintings or a new large animal fossil or new species related to man.

If you are a sick perv. then perhaps a burial site for the bodies of a modern day serial killer.

Most probably, would be damp musty air, bugs and bats/bat dung, vandalistic graffiti, trash  and puddles of polluted water, along with a good chance at a respiratory infection.

Bats, dripping water, maybe some cave drawings of animals or hunting scenes. Bones from animals. Perhaps remnants from a fire. Maybe arrowheads.

The exit after you get lost .

Photo opportunities.

These are kind of cavey.

https://www.flickr.com/photos/31668947@N02/albums/...

A stash of gold ingots from a bank robbery.

I'd say an Alien Mummy but someone would hurt me to get it away from me so  instead I would like to find a burlap bag inside a waxed canvas bag that had inside a handwritten letter by Thomas Jefferson and 10 -1794 'Flowing Hair' Silver Dollars.

A huge vein of gold running through a wall

Stalamites and Stalactites.