The National Portrait Gallery holds the most extensive collection of portraits in the world. It was the first portrait gallery in the world when it opened in 1856. The gallery houses portraits of historically important and famous British people, selected on the basis of the significance of the sitter, not that of the artist. The collection includes photographs and caricatures as well as paintings, drawings and sculpture. One of its best-known images is the Chandos portrait, the most famous portrait of William Shakespeare although there is some uncertainty about whether the painting actually is of the playwright.