It is well worth spending a night or two in Berchtesgaden to take a full day tour with https://www.discover-eagles-nest.com/.
While your at it, our favorite restaurant on our trip to Austria was in Berchtesgaden, Gasthof Watzmann.
My review of our tour:
I'd give Tom a 10 if I could! I found Tom's website while looking for a private Eagle's Nest tour last summer and was very impressed with the content and detail. In September, that detail and enthusiasm were personified when we met Tom and he brought history to life for us as we drove us up Obersalzberg Mountain in the Bavarian Alps. On the mountain we were transported back in time with Tom’s stories, enhanced by the incredible tablet slideshow he created. Our tour included the site of Hitler’s residence, the Berghof, in Obersalzberg, which you don’t get to visit with other tour groups, as well as the incredible bunker system and the opulent Eagle’s Nest. Tom provided insights we could have only gotten from someone with a deep knowledge, love, and passion for WWII history and the area. What a fantastic day! I highly recommend this tour to friends and family! https://www.discover-eagles-nest.com/