WWII Sites and Museums in Northern Germany

Just a few:

• U-995: submarine type VII technical museum in Laboe (close to Kiel)
• Wilhelm Bauer: submarine type XXI in Bremerhaven
• Tank museum in Munster (not Münster)
• Historisch-Technisches Museum Peenemünde, ex V2 development and test center
• Flandernbunker: memorial and exhibition in Kiel
• Danish North Sea shore has various bunkers of Atlantic Wall incl. Bunkermuseum Hanstholm and Tirpitz bunker
• Not able to visit or see are the 1.6 million tons of bombs and munition which still lie in German territorial waters
• Not able to visit or see is Operation Regenbogen (article in German by NDR, North-German public broadcaster); links to some more articles at the bottom

Also former concentration camps and related memorials?

try and find the repurposed Flak bunkers around Hamburg. Their history and what became of them is very interesting.

The Bergen-Belsen Memorial (https://bergen-belsen.stiftung-ng.de/en/) would be a thought-provoking site in northern Germany. I recently finished The Many Lives of Anne Frank (https://yalebooks.yale.edu/book/9780300248128/the-many-lives-of-anne-frank/) by Ruth Franklin, the third and best biography of Anne I have read. The work contains material on Anne's last days at Belsen based on accounts of fellow prisoners. Accounts of the British Army's liberation of the camp are compelling. There's a dedicated memorial for Anne and sister Margot at Belsen.

In Kiel, there is a WWII Bunker (https://ahoi.kiel-sailing-city.de/en/kiel-sailing-city/wlan/detail/POI/p_100045002/flandernbunker). It has been turned into a museum. It is all in German and finding someone to speak English was a bit of a challenge. Also watch your head, there is rebar that you could run into. Even with my broken German I still learned a lot from the exhibits. One of the exhibits while I was there was HS students interviewing elders that lived through the war as civilians. Their stories were very eye opening. We had a car, so I don't know how easy it is to get there without one.

In Hamburg itself, be sure to visit St. Nikolai. The spire is all that’s left of the church above ground, but beneath is the exhibit about the firebombing of Hamburg.

The tank museum in Munster is a bit of a pain to get to by public transit, though it’s still possible.

I'd second the advice to visit St. Nikolai in Hamburg. In addition to the actual bombing of Hamburg, there is information about Germany's attempts to prepare for such attacks and the attitudes of civilians. If I remember correctly, there was even a family-appropriate board game to teach responses to bombings.