West of the National Museum lies the commercial heart of the city, the Centrum crossroads from which ul. Marszałkowska, the main north–south road, cuts across al. Jerozolimskie running east–west. Towering over everything is the Palace of Culture and Science, a post-World War II gift from Stalin whose vast interior now contains theatres, a swimming pool and a nightclub. The platform on the thirtieth floor (daily 9am–8pm, Fri & Sat till 11pm; 20zł; pkin.pl) offers impressive views of the city.