The retreat known as the Eagle's Nest, built for Adolf Hitler in the Bavarian Alps, was almost completely destroyed by fire, and authorities said work to extinguish the blaze was still underway Saturday. A suspect was detained.
The local tourism authority said it wasn't immediately clear whether authorities could salvage parts of the building. Police later said it burned down almost completely.
A fire alarm at the building in Germany's southeastern corner, in the Berchtesgaden district, went off at about 9:15 p.m. on Friday, police said in a statement. Firefighters arriving on scene saw flames as they approached the site, on a cliff 1,834 meters (6,017 feet) above sea level.
Getting fire engines to the site was difficult because of its location, and crews were still working to put out the fire on Saturday morning, police said. The building and its immediate surroundings could only be accessed with respiratory protection equipment.
Firefighters found no one in the building, and authorities believe no one was injured.
Police said they detained a person who came into investigators' focus shortly after the fire broke out, but it has yet to be determined whether they had anything to do with the fire.
The building, the Kehlsteinhaus, was completed in 1938 and is reachable by elevator from the end of a road that winds up the mountain, partly through a series of tunnels. The road is closed to public traffic but used by buses for visitors.
It has been operated as a cafe and restaurant since 1952 and contains an exhibition on its history. It was not open on Friday before the fire broke out.
