Answer the following question: I want to test the ability of students to read a passage and answer questions about it. Could you please come up with a good question for the passage "The music hall and cabaret are famous Paris institutions. The Moulin Rouge was opened in 1889. It was highly visible because of its large red imitation windmill on its roof, and became the birthplace of the dance known as the French Cancan. It helped make famous the singers Mistinguett and Édith Piaf and the painter Toulouse-Lautrec, who made posters for the venue. In 1911, the dance hall Olympia Paris invented the grand staircase as a settling for its shows, competing with its great rival, the Folies Bergère, Its stars in the 1920s included the American singer and dancer Josephine Baker. The Casino de Paris presented many famous French singers, including Mistinguett, Maurice Chevalier, and Tino Rossi. Other famous Paris music halls include Le Lido, on the Champs-Élysées, opened in 1946; and the Crazy Horse Saloon, featuring strip-tease, dance and magic, opened in 1951. The Olympia Paris has presented Edith Piaf, Marlene Dietrich, Miles Davis, Judy Garland, and the Grateful Dead. A half dozen music halls exist today in Paris, attended mostly visitors to the city."?
Answer:
What happened in the 11th year of the 20th century?