Located just behind Seattle’s bustling Pikes Place Market, Post Alley is a popular quick stop for tourists. Eccentric paper and spray-painted graffiti adorns brick buildings on one side of the alley, while thousands of individually-placed pieces of chewing gum make up the 50 ft-long Market Theater Gum Wall on the other side. Originally begun in 1993 by theatergoers of the improv comedy group Unexpected Productions, the gum wall became an official tourist attraction in 1999 after theater workers tried scraping the gum off twice but eventually gave up when it kept reappearing. At one point there was even a strategically placed gumball machine right outside the Market Theater box office, although unfortunately this has since been removed. Still, the wall continues to grow, so bring your own Bubble Yum and stamp your place on this sticky, colorful attraction.