Drain mystery: What is it?

[clunky]

I'm starting to remodel a basement bathroom. After removing the old sink and vanity, I discovered this drain access/opening (see photo) that was hidden under the cabinet. What is it? Was a toilet located here sometime in the past? Actually, I wouldn't mind locating the new toilet here, if that's what it is.

Thanks for any advice you have!

 

[Jadnashua]

Most likely, it's a sewer line cleanout.

 

[Sponsor]

 

[clunky]

Most likely, it's a sewer line cleanout.

Thanks...kind of what I expected. Guess I'll leave it be.