Ground plan of a house: second century AD
This was a novelty when it was published in 1957, and nothing comparable has been discovered since. The plan shows three main areas, possibly courtyards rather than rooms. The central one is described as an atrium, and from it a staircase descends to a cellar which was probably vaulted. At 90°, a row of parallel lines would represent a staircase on a modern plan, but that may not be the right interpretation here. A boxed rectangle adjacent might be a water-tank, or a central staircase-well with the parallel lines marking a stair to an upper floor; the stair down to the cellar, already mentioned, would then turn a right-angle and continue down underneath the upper flight.
The Oxyrhynchus Papyri vol.XXIV no.2406