The East Side Gallery is a 1.3 km long section of the Berlin Wall located in the Friedrichshain-Kreuzberg district of Berlin. This open-air gallery features 105 paintings by artists from all over the world, making it the largest open-air gallery in the world
From Wikipedia
The East Side Gallery memorial in Berlin-Friedrichshain is a permanent open-air gallery on the longest surviving section of the Berlin Wall in Mühlenstraße between the Berlin Ostbahnhof and the Oberbaumbrücke along the Spree. It consists of a series of murals painted directly on a 1,316 m (4,318 ft) long remnant of the Berlin Wall, located near the centre of Berlin, on Mühlenstraße in Friedrichshain-Kreuzberg.