Discarded seed pod. A dried-out fig, maybe? It was under an olive tree, but it's definitely not an olive!
Best guess: a squirrel or something grabbed it from another yard and didn't finish it before scurrying off.
@kelsonv Pomegranate maybe?
@artsyhonker @raye Yeah, I think that's it. Thanks!
@kelsonv I'm with artsyhonker on this, especially when you look at the navel on the rind. That's fantastic.