Okay. You said it was like ten inches down, so I'd guess it's probably not something related to your house, it's probably some bit of infrastructure from the old street. Which means we should be thinking in the realm of "outside municipal access covers", and not "something installed to make my house better".
10” isn’t all that deep. 4-6” slab with some subgrade. That’s 10” and would be about the depth for backflow preventers. Which that likely isn’t. But depth means nothing.