The British Museum is a museum in London devoted to human history and culture. It has an extensive collection of over 8 million works from across the world. The museum was established in 1753 based on physician Sir Hans Sloane's collections. It has expanded over the centuries as a result of Britain's colonial activities. Some exhibits, like the Elgin Marbles, are controversial and calls have been made for their return. The Lewis Chessmen were discovered in 1831 in Scotland and date back to the 12th century, making them some of the few surviving medieval chess sets. They are now owned by the British Museum and National Museum of Scotland.