Large outdoor music festivals in the summer and autumn are popular, such as Glastonbury, V Festival, and the Reading and Leeds Festivals. The most prominent opera house in England is the Royal Opera House at Covent Garden. The Proms – a season of orchestral classical concerts held primarily at the Royal Albert Hall in London – is a major cultural event in the English calendar, and takes place yearly. The Royal Ballet is one of the world's foremost classical ballet companies, its reputation built on two prominent figures of 20th-century dance, "prima ballerina" Margot Fonteyn and choreographer Frederick Ashton.