Czechia's entertainment culture is built on a foundation of classical music and beer hall culture that together constitute two of the most serious leisure traditions in Central Europe. The Prague Spring International Music Festival, held each May in the city's concert halls and churches, is one of Europe's most prestigious classical music events and opens annually with a performance of Smetana's Má vlast (My Homeland). The Karl Marx theatre tradition — Czechoslovakia's theatrical heritage, which produced internationally significant directors and playwrights including Václav Havel — continues in Prague's Národní Divadlo and the smaller experimental venues of the Žižkov district. The Colours of Ostrava world music festival and the Pohoda festival in Slovakia (accessible from Czech Republic) extend the summer entertainment calendar. Czech opera, Czech jazz in the Reduta and Jazz Dock clubs, and the pub music tradition of pívnice evenings add the everyday entertainment register.