I juggled around a pile of Discovery ideas... here's a list of basic ideas I had, steal anything you want:
Exploring the ocean, sail around to see what's on different islands
Same concept in space
Archaeology, dig into the ground and find fossils or gold or something
Alchemy, mix together ingredients and see what potions you make
Roguelike cave kinda thing, dark, but as you move around it's mapped
The "discovery" phase of a trial - that's when you tell the other side what documents they have to share with you. Why that would be interesting is unknown.
It COULD be interesting if they refused to provide, and so you broke into their building and snuck around stealing the documents. But that marginally fits the theme only by name.
Disco, Very! Don't ask me what that is other than an out-of-sight dance party circa 1978.
Science! Research to invent amazing new things.
And last and probably least is the one that came into my head almost fully formed. The problem is only that it is pretty much for 3-year olds. A simple idea is good for LD, because you can get it done. The bad thing is if it's not actually fun. And this isn't yet, but I haven't tried adding the cranky tiger. Have a look at the very rough cut (no win or lose features included) of Cranky Tiger, Hidden Panda:
That is playable! Give it a try. That's all temp art, of course. Pandas aren't just white.