A method for assembling a modular auditorium and modular auditorium. The method includes providing a plurality of nominal inventory portions. Each nominal inventory portions includes a prefabricated base portion, and a prefabricated tier section for assembly to the base portion. The prefabricated base portion is positioned on a ground surface of a public performance space. The prefabricated tier section is fastened to the prefabricated base portion to form a self supporting modular auditorium structure that does not require lateral support from a building structure other than the ground surface.