heres a close up, its just a brick rectangle with a hole in it, the base concrete slab also has a hole in it and the inside is cover with thick black plastic to stop moisture going out through the bricks.
That ugly front side mortar you see there will be hidden once I place the calapsable side wooden benches onto the bricks, calapsable so they don't take up space when not in use but that extra shelf space will be great come party time.