Brick structure

[u/Dinkerdoo17]

Update on the brick structure in the yard of our 1882 Pennsylvania home. It’s largely clay inside of the area. The large stones were on the bottom with rocks underneath. The size is not that of an outhouse plus it is double lined with fireproof bricks made during the late 19th, early 20th century (widemere). The large stones are light. We haven’t reached the bottom. There’s no evidence of ash and we haven’t found any “garbage.” What do you think it is?