This looks like the beginnings of some kind of art installation. Because we are doing a slab on our entire first floor, we needed to layout all of our sewer drain lines first. The tall pipes are set up to "test" the system and will be removed in a day or so.
This crazy business is under the floor of the bathroom in the ADU (Accessory Dwelling Unit, aka Mother-in-law unit). The diagonal line is the kitchen drain coming in. The lowest is the tie in from the second story bathroom which then heads out the foundation wall. There is a backwater prevention valve in the upper run above the loop. The manhole out in the street is higher then our first floor toilet, so a special valve had to be installed to prevent an ugly situation if the street sewer ever overflowed.
Above is our second story drainage to the left and our laundry room drainage to the right.