When our house was built 5 years ago a basement bathroom had rough-in plumbing. What we have is a toilet flange, a 2 foot lavatory pipe coming up through the concrete and a square cutout in the concrete approximately 9 inches across. This square cutout is covered with a black plastic domed covering. I recently poked through this domed covering to see what was inside. All I saw was the plastic vapor barrier beneth the concrete and the gravel beneth the vapor barrier. Is this normal? I think I was expecting to find something other than an empty hole under the domed covering. Thanks for your help.

The square hole is a tub dap-out. Dig around it and look for a horizontal pipe that's capped off. It should be down there somewhere. Regards, Tom