The Prule apartment houses were built for academic staff of the University of Ljubljana. This building represents the first of a series of similar interventions in the style of Edvard Ravnikar. Kristl has introduced a range of simple but innovative solutions for collective housing. Flats have a minimum surface and are designed to be as economical and flexible as possible. That allows a variety of arrangement of flats. Kristl inserted a corridor to separate living and sleeping areas. The stairwells has small balconies which illuminate the hallway and allow ventilation.