Imperial War Museum, Duxford, Cambridgeshire http://duxford.iwm.org.uk
The Museum occupies the former RAF fighter base, using many of the original buildings as well as newly built ones like the American Air Museum. It is not just a museum exhibiting a collection of aircraft, many are still flying and one of the hangers features aircraft being maintained or restored. There is also the Land Warfare Hall featuring many historic military vehicles, guns and tanks, including the replica Tiger constructed for Saving Private Ryan and also used in Band Of Brothers.
The range of aircraft is predominantly military, mostly British or American, covering WWI to the recent past and including such iconic planes as Spitfires, Hurricanes and Mustangs with the American Air Museum housing a B52 bomber and an SR 71 Blackbird, dwarfing everything around them. The collection of civil aircraft includes one of the Concorde pre-production test aircraft and British airliners such as the BAC 1-11, Bristol Britannia, Vickers VC10 and Viscount some of which are open to visitors.
Being a former RAF base the site is very large but it is all on a level except the entrances to the American Air Museum and the Land Warfare Hall. Mobility buses run along the entire site for those who find it too far to walk with wheelchairs and electric mobility scooters also being available to those in need. Picnic benches and seating are scattered throughout and there are also catering facilities should you prefer.