Underneath the streets of London lies the London Dungeon. One of the scariest attractions in London, it has been open since 1976 and has progressed from simply being a museum detailing historical events to interacting with the visitors and uses more special effects to entertain the visitors.
Upon entering the Dungeons you are sentenced to your own death for various strange crimes and then taken on a trip throughout history. The Dungeons use various attractions such as Traitor: The Boat Ride to Hell and historically related attractions to draw in the crowds like the Sweeney Todd attraction.
Avoid the queues by booking fast track tickets in advance.