Bought his house this summer. Didn't like that pool liner attempted to float in a few areas during a 2 day ice storm back in October with 3+ inches of rain. Back corner around shed became a lake with water seeping into shed. I'm thinking of installing a sump. Might put a drain hose down this hole if it's just drainage however my gutters just drain onto concrete and I don't see any outlets for drainage in street. This pipe goes down about 4 feet and appears to have been installed at the same time as the concrete about 10-15 yrs ago. 4" pvc/no lid.
Probably a place to insert a umbrella pole
It's randomly located so likely not a drain. Any water that near the pool would likely drain into the pool.
Edited to add this picture as an example of one, and a link to the seller