A Visit to The Imperial War Museum
The museum is located in the slightly down-on-its-luck Lambeth Road neighborhood in the afore-mentioned Bethlem Royal Hospital (formerly the dreaded "Bedlam" insane asylum of history). The building is brightly-lit and makes for a pleasant visit that's neither too much nor too little, and begins outside with two 18-inch naval gun tubes and a shell (the author is seen standing next to it to show relative size). A piece of the Berlin Wall to the left of the entrance is actually about as much that can be seen in Berlin (as the rest of my trip proved).
Inside on the ground floor is a mix of vehicles that include a Jagdpanther (complete with the holes in its side that knocked it out of combat), a Sherman Mk. V, a T-34/85 and several artillery pieces, including the famous 18-pound field gun.
On the second floor is an exhibit dedicated to the air war that includes a Focke-Wulf 190 and a P-51. If you want aircraft, though, the place to visit is the RAF Museum in Collindale.
The basement has a huge collection of relics from World War I to the post-WW II conflicts, along with the "Battle of Britain" tour that includes a "blast" from a near-miss bomb.
And when you're finished, be sure to try some of the "Blitz" cooking in the museum's restaurant, including Shepherd's Pie, Mac & Cheese, and Beetroot & Chocolate Cake.