Ballet & Opera
Prague has three main venues for opera, ballet, and concerts: The National Theatre (Narodni Divadlo), the Prague State Opera, and the Estates Theatre.
The price for tickets is a lot of times much cheaper than in other European cities. Book your tickets in advance, straight on the website. Go to: www.narodni-divadlo.cz/en
Oh and keep in mind that people like to get dressed up for Dress at least smart casual (not in jeans and sneakers) to fit into the crowd.