John Lennon became a symbol of pacifism and a hero of sorts for young Czechs in the 1980s. After his assassination, an image of him + Beatles lyrics were painted on a wall.
The secret police repeatedly tried to whitewash it, but never managed to keep it clear for long. Political messages and images continued to be added. Though the original John Lennon image has eroded away and been covered up, it continues to draw art, messages, and random graffiti from locals and tourists alike.
It’s no longer whitewashed, but is an ever-evolving piece of public art.