Help identifying waste line opening

I just noticed this open-ended part of a waste line in the basement of a house I just bought. Any idea what it is and/or why it would be open? (Pictures keeps rotating when I post them) Attachment 43649 (http://www.doityourself.com/forum/attachments/plumbing-piping/43649-help-identifying-waste-line-opening-image.jpg) Closeup pic of the opening Attachment 43650 (http://www.doityourself.com/forum/attachments/plumbing-piping/43650-help-identifying-waste-line-opening-image.jpg)