Some weird old guy in a dusty suit hands you a key and wanders off mumbling about the Fountain of Youth. The key has an address stuck to it with some mangy looking tape. It’s actually not far from your place. But when you get there it’s just an empty lot. Still, now that you’re here you decide to sit under the trees and read a book awhile. It looks peaceful and the shade would be great on such a warm day.
One of the trees has a metal plate on it. In the middle is a gap, just the right size for your key. You put the key in and give it a turn.
Somehow, you’re not totally surprised to find the tree opening up to a glowing path, descending down, way underground. What’s down there, when you finally get there?