Sofia concentrates the majority of Bulgaria's leading performing arts troupes. Theatre is by far the most popular form of performing art, and theatrical venues are among the most visited, second only to cinemas. There were 3,162 theatric performances with 570,568 people attending in 2014. The Ivan Vazov National Theatre, which performs mainly classical plays and is situated in the very centre of the city, is the most prominent theatre. The National Opera and Ballet of Bulgaria is a combined opera and ballet collective established in 1891. Regular performances began in 1909. Some of Bulgaria's most famous operatic singers, such as Nicolai Ghiaurov and Ghena Dimitrova, made their first appearances on the stage of the National Opera and Ballet.