A group of climate activists sprayed paint on the Brandenburg Gate in the German capital of Berlin on Sunday, calling for urgent action against climate change.
The group posted a photo on social media showing its members spraying orange and yellow paint on columns of the landmark using what appeared to be fire extinguishers.
The photo shows the pillars and other sections widely covered by the paint.
Police detained 14 people at the scene, and launched an investigation into property damage.
One of the detainees said it is obvious that people should stop using fossil fuels by 2030. The group is demanding that the German government take urgent action against climate change.
The Brandenburg Gate was built in Berlin more than 200 years ago.
Access to the gate was prohibited when the country was divided into East and West Germany. It became a symbol of reunification after the Berlin Wall fell in 1989.
Speaking to local media, the mayor of Berlin, Kai Wegner, said, "With these actions, this group is not only damaging the historic Brandenburg Gate, but also our free discourse about the important issues of our time and future."