It is at the center of a small island. You can spot this island easily from distance. What makes it differ from its surroundings is one large, old, stone compound. Its central part is circular and it’s surrounded with large stone arches. Couple of palm trees are scattered on the island.
Quest that takes you toward this area can be acquired from a small runestone fragment. This small rock is found on the shore, just northeast of this compound, west of nearby “The Lord” mundus stone.
Sand Kingdom Moons - Super Mario Odyssey Power Moons