Behind Seattle’s Pike Place Market, lies the Seattle Gum Wall.  This tacky tradition began in 1993, when patrons to a local comedy club would leave used chewing gum & small change attached to a brick wall outside the Market Theatre. Twice the theatre tried to scrape the gum away, but the tradition “stuck” and was deemed a tourist attraction in 1999. It has since grown in size and popularity. Tourists and locals come to gawk, take photos or add their own gum wad to this expanding art project – sometimes spelling out messages or designing symbols out of this sticky medium.  Disgusting? Yes. Interactive? Also yes: completely participatory urban art!