By all means visit the State Academic Opera and Ballet Theatre. Furthermore, Chapel of St. Nicholas and the Alexandre Nevsky Cathedral (Sobor Alexandra Nevskogo) on the Krasny Prospekt, and the Cathedral of Ascension (Voznesensky Sobor) on the Ulitsa Sovetskaya are also a must-see. Novosibirsk Zoo is definitely worth visiting if you're travelling with family...