We’ve been in the house for a few months. Its a 1970s 2 floor colonial with crawlspace under house and slab under garage.

I went down there to crawl around and see whats going on when I saw things I am unfamiliar with.

1—is this big hole in the wall below fireplace, where a metal duct cap was lovingly shoved into the wall. This is surrounded by, what appears to be fragments of broken chimney liner on floor. One of the previous owners had the whole chimney rebricked and mortared when it fell away from the house in a storm. I would think this is some sort of ash dump, but the fireplace upstairs doesnt have a hole in the base. The fireplace and the bottom of the fireplace opening in the family room is solid brick, pictures of chimney, fireplace and crawlspace mystery (last few pics on bottom)

Any ideas would be appreciated.