And before photography, survey drawings, plot plans, etc.

The only place you could get away with “built something over it” is a remote location where people people don’t hang around. Or a military base not required to follow normal, civic regulations.

You could guess it was something built in antiquity, but construction in those times could take generations (e.g. cathedrals). Anything built hastily would use material that degraded quickly, or collapsed (e.g. rapidly constructed stone walls tend to get out of plumb and fall down).

Edit: by remote location I also mean a place no one would think up request satellite imagery of. If it were in a snow covered location maybe you could cover something with white tarps then build a structure over it but even the most elementary of large buildings require trades people to do anything. How many? Lots. Or it takes forever and that in itself is a problem.

There’s another possibility here. The object could have been found in a mine. You could imagine closing a mine down very quickly and sending everyone home because it was unsafe for some plausible reason. Then you build a security perimeter around it (fencing to keep people out, it’s unsafe). Then you add surveillance and wait until the world forgets. Still you eventually need to have people going back in. And we are back to the original problem.

While I do think it’s possible there’s a building like this, I think we’ll be surprised when it’s revealed (I am not holding my breath).