Adolf Hitler's Alpine mountain retreat, known as the Eagle's Nest, was engulfed in flames on Friday night while police arrested a 33-year-old male suspect.
The residence, called the Kehlsteinhaus, is above the town of Berchtesgaden. It was one of several buildings in the area used by the Nazi dictator and his entourage during World War Two.
Hitler also used the area as a backdrop for propaganda films portraying him as a lover of animals and nature.
Local media reported that site had been "largely destroyed", with the public urged to avoid the area.