Graffiti Art has blazed a trail across the world, with amazing examples visible in every modern city, but its pioneers were the New Yorkers who painted whole subway cars. For a few years in the 1970s and '80s, their creations made New York's subway system a unique, constantly evolving gallery of a new art form - a visual counterpoint to hip-hop and rap music, and a powerful expression of urban culture. It couldn't last; the city authorities made powerful efforts to stop the artists, but their visual inventiveness has left a permanent mark on the urban art landscape.