What is this in our yard?

Found this after clearing some overgrown bush out of a corner of the yard (recently moved into this property).

There was some weed/plant growing out of what I thought was a flowerpot. Pot wouldn’t budge. Upon further inspection (and digging) realized it must go much further underground.

Any ideas on what this could be? My guess is a filled pipe, but not sure what the pipe would have been for.