Looks like the asphalt slopes toward it which would direct stormwater into it. There's also no gutters on the building in the back, so that water would just hit the pavement and run off. There's also a pump-looking gizmo in the lower-right corner that appears to have a discharge hose going away from the structures on the property.
Or for propane tanks. They need to have an area underneath to catch the gas if they star leaking. And the bumps can be some kind of foundation for putting the tanks. It looks like it could hold two tanks next to each other.
If you have something that looks like a pool they’ll go swimming.
The ladder gets them out and the humps give them a place to stand in the middle to keep their heads above the water line. Their arms get tired very quickly.
It looks DIY, so I'm willing to accept the ladder. The humps are a bit of a mystery, but from the look of the dirt between the asphalt and the pond, I can see them being sediment buildup from the runoff. Not sure why they're in those configurations, though, but that'll have to remain a mystery for someone else to solve lol.