Old Coal/Wood Water Heater?

mdangelo

I'm getting ready to pour a new garage concrete slab and think I found an old foundation with some sort of steam water heater embedded in the wall. I was curious if anybody has any idea what it is. I'd like to dig it out and perhaps save the face but just want to make sure I'm not unearthing something that should stay where it is. By the way, the inscription on the door may be hard to make out from the pictures but it says "Union Steam Water Heater" Thanks!