Berlin to Eagle's Nest

No. it is too far for a day trip. I was thinking if you stay in Munich or Salzburg instead of Berlin
https://www.eagles-nest-tours.com/

The Eagle's Nest is pretty nondescript, purposely kept that way, and is more of a mediocre restaurant than a homage to Hitler. I don't think a day trip is possible from Berlin, it's too far away. A trip from Munich or Salzburg is easier.

Personally I'd rather spend my time exploring Salzburg and from the Hohensalzburg Castle you have a fine view of the Eagle's Nest and surrounding mountains.

df,

A day trip from Berlin to Berchtesgaden is absolutely out of the question. Travel time by train is about 9-10 hours EACH WAY.

A couple of choices you could consider......

• change your post cruise location from Berlin to Munich.
• visit WW-II sites near Berlin instead, such as Sachsenhausen, Wannsee, Potsdam or walking tours in Berlin (the Original Berlin Walks has some excellent tours).
• you could perhaps take a day trip to Dresden, which is a very historic city. The Cathedral there is magnificent, and there's also an excellent military museum.

There is absolutely no need to fear that you will get bored spending four days in Berlin. If you are interested in WW II sites and museums, Berlin really has an amazing lot to offer, plus all the other sights. And, as the others said, the Eagle's Nest is way too far as a day trip.

than a homage to Hitler

If there's one thing we don't need, it's a homage to Hitler. We can do very well without the sort of pilgrimages that tend to go along with that kind of commemoration.

I suggest staying in Berlin for the 4 days. There is so much to see/do in Berlin that 4 days won't be time enough. We visited the Eagle's Nest on a day trip from Salzburg, taking the excellent tour recommended in RS guide. While we found it interesting, and the views from the actual Eagle's Nest are beautiful, I do not think it is worth taking time away from your stay in Berlin.

Stay in Berlin to see the war related sites there...lots of them if you know where to look and go.

See the resistance Museum, or the Invalidenfriedhof off of Invalidenstraße, exiting from the Berlin Hbf. Go to the British military cemetery on Heerstraße on the RAF members shot down over Berlin in their strategic bombing campaign.

Take the train from Hbf to Frankfurt an der Oder, change to the S-Bahn to go to Seelow to see the memorial and museum (Gedenkstätte Seelow Höhen) on the biigest battle fought on German soil, when the Russians launched their frontal offensive against Berlin, only to be stopped at Seelow the first day. What about the Flaktürmen at Berlin Gesundbrunnen?