Saracen Tower was a large residential tower for Citizens in the city of Mendel on the planet Mesa, nine hundred meters in diameter and one and a half kilometers tall. The building was a honeycomb of fifty meter wide ceramacrete tubes arranged in cells which ringed a central core. Its central cell consisted of six tubes arranged in a ring around a central air shaft which also gave access to small air cars. Outside was a large atrium, thirty meters across, with pedestrian ways and traffic lanes. Suspended pedestrian and vehicle ways crossed it at regular intervals. A second ring of cells, each identical to the central core, threaded around the atrium, surrounded by another atrium and yet another ring of cells.