Twickenham Stadium is the largest dedicated rugby union stadium in the world, seating 82,000 people, and the home of England rugby since 1909. On match days — particularly for the Six Nations or autumn internationals — the whole town transforms. The approach from the train station is wall-to-wall white shirts, the pubs overflow, and the atmosphere is boisterous but good-natured in the way that only a sport which hasn't fully professionalised its fanbase can be.
On non-match days, the stadium offers behind-the-scenes tours that take in the players' tunnel, changing rooms, the Royal Box, and the World Rugby Museum in the south stand. The museum covers the history of rugby union from its origins at Rugby School through to the modern professional game, with a good collection of memorabilia and some decent interactive exhibits. Tours need to be booked in advance.