Marinsky II, the $700-million theater and concert hall that opened in 2013 after a decade of planning and construction, is a must-see in St. Petersburg. The old Mariinsky, which is on the other side of the Kryukov Canal, is reflected in the Marinsky II's facade of glass and beige Jura limestone (a pedestrian bridge connects the two). Holding up to 2,000 people, this amphitheater is often used for concerts in the summer, especially during St. Petersburg's famous White Nights Festival. The interior is very elegant, with much use made of wood, glass, marble, and Swarovski crystals (for chandeliers and other lights). If you plan on attending, be sure to familiarize yourself with the long list of rules of conduct on the theater's website.