Built by James Bedlam in 1812-1821 and later had an impressive dome placed on top by Sydney Smirke in 1846. Prior to becoming the war museum the building was the Bethlam Hospital for the care of the mentally insane.

Outside the museum there are two large naval guns, which used to fire shells of 875kg, reaching a distance of 30km.

As you enter the building you can see biplanes, fighter planes and a V2 rocket hanging from the ceiling. The museum has a central floor covered in tanks, field guns and a small submarine, from World War II and the Great War. There are showcases of equipment, relics, paintings, books, photographs, and films relating to all three armed forces. Also within the museum are the Trenches and Blitz experience. One of the nicest but saddest displays are the ones that tell the story of war from the ordinary soldiers point of view, with personal letters to loved ones being used to help give you an insight.