Poland, Auschwitz-Birkenau State Museum, Auschwicz Concentration Camp, Entrance gate with 'Arbeit Macht Frei' slogan.

Poland, Auschwitz-Birkenau State Museum, Auschwicz Concentration Camp, 'Arbeit Macht Frei' slogan above the entrance gate.

Poland, Auschwitz-Birkenau State Museum, Auschwicz Concentration Camp, 'Arbeit Macht Frei' slogan above the entrance gate.

India, Maharashtra, Mumbai, 'Art wall' covered with slogans, graffiti and drawings to encourage Mumbai people to be positive and upbeat and anti-terrorism.

India, Maharashtra, Mumbai, Muslim man walking past an 'art wall' covered with upbeat, positive slogans and images, with the theme Long Live Mumbai.

Germany, Berlin, The East Side Gallery, a 1.3 km long section of the Berlin Wall, Mural by Jolly Kunjappu called 'Dancing to Freedom'.

Germany, Berlin, The East Side Gallery, a 1.3 km long section of the Berlin Wall, Mural known as Save our Earth by Artist Indiano.

Germany, Berlin, The East Side Gallery, a 1.3 km long section of the Berlin Wall, Mural known as Save our Earth by Artist Indiano.

Germany, Berlin, The East Side Gallery, a 1.3 km long section of the Berlin Wall, Mural known as 'Save our Earth' by Artist Indiano.

Germany, Berlin, Potzdamer Platz, Preserved Berlin Wall section with political message.

Ireland, Derry, The People's Gallery series of murals in the Bogside, Mural known as "The Petrol Bomber".

Ireland, Derry, The People's Gallery series of murals in the Bogside, Mural known as "Civil Rights".