Adolf Hitler's historic teahouse, known as the Eagle's Nest, went up in flames on Friday evening in southern Germany, with police suspecting arson and arresting a man, local media reported on Saturday.
Emergency services were alerted shortly after 9 pm local time (1900GMT), prompting a major firefighting operation, German newspaper BILD reported.
The building, officially known as the Kehlsteinhaus, was already engulfed in flames when firefighters and police arrived, according to police.
A police spokesperson told the newspaper that officers suspected arson.
Police said officers responding to the fire encountered a motorcyclist travelling in the opposite direction.
The officers alerted firefighters before stopping and arresting the man, according to police.
Authorities have yet to determine whether the arrested man was involved in starting the fire, while the cause of the blaze remains under investigation.
No injuries were reported, and initial findings indicated that nobody was inside the building when the fire broke out.
Firefighters continued battling the blaze late on Friday, while the extent of the damage remained unclear.
The Kehlsteinhaus was built in 1937-38 as a representative teahouse for Nazi leader Adolf Hitler at an altitude of 1,834 meters (6,017 feet) above sea level.
The building was intended to host foreign dignitaries and serve as a political reception venue away from public view.
