A: "It also looks to me like there is a section of cement at the bottom that is significantly older than the concrete blocks. (But it might just be dirtier) Is it possible that this exact spot once housed an older structure? If that’s the case, I wonder if there was once a cistern there, under an older house. When the garage was built, there was an original intention to keep the cistern, but it was later filled in for safety reasons. That would explain the access gaps left behind that look large enough to run pipe but don’t have any."