I am looking into having a bathroom put into my basement in a new 'old' home. I have one pipe in the basement that is perplexing. In the first picture I have marked the plumbing coming down from the sink upstairs on the left, a pipe in the back of the basement, about 4" wide and capped with concrete perhaps, and a floor drain to the front of that. Would the larger 4" drain in back be a roughed in drain for a toilet that was never used? In picture 2 i have my washer dryer hookups and washer lines, however, in pic 3 im not exactly sure what I have there? Im wondering if it was plugged just to prevent sewer gas smell beings it was never used. Any help would be appreciated.