Once the performance has started, the entry of delayed audience members is subject to the program: Approximate duration is 2h 25 minutes with a 15-minute intermission. Tosca is an opera in three acts, with music by Giacomo Puccini and an Italian libretto by Luigi Illica and Giuseppe Giacosa. It is considered one of the most representative operas of the Italian verismo repertoire, due to its dramatic intensity and for containing some of the most beautiful arias in the repertoire. World premiere: Rome, January 14, 1900, at the Teatro Costanzi. Premiere in Mexico: July 1901, at the Teatro Arbeu. Premiere at the Palace of Fine Arts: March 1935.