Time Out says
Definitely one of the weirder roadside attractions in not only SLO but all of California, this near-hidden alleyway between between Broad and Garden streets is its own sort of graffiti wall. It's impossible to say just how many pieces of gum now stil to the 15-foot-high and 70-foot-long walls, but residents and visitors have been sticking globs of multicolored gum onto this alleyway since the early '70s. Grab some ammo from the nearby Powell's Sweet Shoppe, then add to it yourself. Be sure to grab a photo once you do—just don't lean too far back.