There is an alley in San Luis Obispo, California where people paste their chewed up gum on the walls. It started in the 50’s and is quite the tourist attraction. There are plenty of sites on the internet with information about this bizarre place. Click here if you want to read more.
There is even gum art!
It grosses me out, but fascinates me, too. I don’t know if I could stand to walk down the alley, though. Just imagining all of the saliva gives me the heeby geebies.