Abstract: An auditorium construction can be interconverted between a level, clear floor in removable sections and an arrangement of a plurality of regularly disposed theatre seats. The separate floor sections can be removed and horizontal, support columns can be swung into a releasably locked vertical position, carrying with them theatre seats moving from a horizontal position into a vertical position. Additional floor panels are then placed between rows of the erected theatre seats and overlying the previously stowed clear floor sections. A reverse operation returns the theatre seats to horizontal position and restores the clear floor.