Agree with many – Duxford, British Museum, IWM but also add:
Pergamon Museum in Berlin. With the freaking gates of Babylon!!!
NASA (Johnson space center) in Houston – Saturn rocket + command centres
Air and Space museum in Chantilly (where Smithsonian puts the planes that don’t fit in DC) – like The Discovery and SR-71
Brooklands in Weybridge – amazing cars, Concorde and great feel for early motor car racing
Minuteman Missile National Historic Site – freaking nuclear missile.amd you can press the button
reykjavik phallological museum – for perspective.