I started peeling up the vinyl floor in the 1/2 bath in my basement. Its concrete underneath but as i continued i found a portion of the floor that was wood. Its about an 8 inch square. the wood was taped in place and supported by a piece of 2x4. I pulled it out and about a foot down the hole is some type of lid with rivets holding it in. there is some concrete debris on top of the lid. there is space around all 4 sides ( about 1/4 inch) where i can sweep some of the dirt . What could this hole be. its near the door of the bathroom but not anyplace you'd want a shower drain to be. This hole kind of has a 'basement' smell. the wood cover had brown mold under it, we did have the bathroom sink overflow a few months ago. Could this be just a basement flood drain.
If the is concrete at the bottom I would guess that it might have been a temperary post while the pored the floor before the built the bearing wall, but I've been wrong before.
BTW, welcome to the site.