Growing up in Chicago I used to spend my teenage summers hanging out along the lakeshore, biking, swimming and sunning. Sometimes I would spend my day at one of the many sandy beaches, but more often than not, I would just bike the length of the rocks along the lakefront.
Those large limestone blocks were put in place in the early part of the 20th century to prevent erosion, but they eventually became a canvas for local want-to-be artists who covered them with cans of spray paint and multi colored paint brushes. This was the Chicago street art of my youth.