A Ksar is a grainery, where people keep there grains from harvest, and other foods, This is a sort of thing raiding parties would come after so un Tunisia berber communities would have a neighborhood Ksar which was were all of the farmers of the district keep there stores and it could be guarded more easily. This one Ksar Ouled was a series of maybe a hundred or so rooms, other double storey around a courtyard on top of a hill - hills being important for defense.
If it looks fimilar it's because, like so many things in Tunisia it was a a filming location for Star Wars - This time it's the Phantom Menance and it represented the slace quarters in Mos Espa where the young and a bit annoying Anakin Skywalker lived before being taken away by some religious nutbags banging on about him being the choosen one, spoiler alert it doesn't end well.
Some of these stairs could do with so occupational health and safety inspections.
