I'm just trying to plan out the bathroom in the basement and need to identify what is stubbed in. The toilet seems obvious and is marked by the flag. The pipe coming up i'm guessing is for the sink drain. However, there is a little square in the bottom right of the photo that i'm not sure what it is. Could that be the p-trap for a shower? Or a cleanout? It looks like some kind of PVC that is partially covered with concrete. Also, there is a big square made with 2x4's that i'm not sure what that is. I'm not sure it's even related to plumbing. Any help would be appreciated.