Colourful, John Lennon Wall.
A nice place to head to (5 min walk from Charles Bridge) and it's certainly a colourful display. The wall has been resprayed a number of times, but it's eclectic to look at and read the graffiti. The atmosphere was good here and it helped that the sun was shining which made everything look even brighter.

There is usually a busker singing (believe it or not!) John Lennon songs at the wall. I felt very sorry for the busker whilst we were there, he was very patient and understanding whilst having endless 'selfie sticks' shoved in his face, people videoing him and people posing repeatedly either in front or at the side of him. Give the poor guy some space (or at least chuck a few CZK in his guitar case!).
Nice place and well worth walking past to say that you've seen it!