It wouldn’t be unusual to find a well here. There were native people living in this area near the river. To construct a Indian well, you just dig below the water table, allow the well to fill with filtered water, and bail the well out until the water becomes clear.
There is a huge mysterious cavity under my living room. Someone actually built stairs to have access to it. They also installed a water heater, furnace, light fixtures and laundry hookups.
My landlord refers to it as a base mint. My guess is that at some point, it smelled minty.