In Belize there is a beautiful blue hole in the ocean which feels like it would make an awesome campaign location.

I’ve been trying to think of how to use it in my campaign and I have a few ideas.

I am thinking this location could be a tiny distance off the coast, and a king could have built his castle on it. It would at the least make a good natural harbor for his personal use.

The other thought I had was that an aquatic species could have taken up this spot as a place to develop a mid ocean trading post almost. I could imagine a big-ish city built on and around this spot where a powerful aquatic nation makes direct and frequent contact with surface dwellers.

My other thought was that this could lead into a massive network of tunnels that lead to the elemental plane of water. Almost like a tangled wormhole bleeding through the ocean floor.

What excellent uses can you think of for this spot in game?