San Luis Obispo, California, has the distinction of being known as the home of what's probably the largest bubble gum alley in the world. While no one knows for sure how the alley started, there are some theories out there, including that it started out as a graduating class event or that it started as a school rivalry. The alley stretches back at least to the 1950s, but it has and still does divide local opinions.
Some see it as an eyesore, while others consider it a work of art. Either way, it's not likely to come down anytime soon, and the 70-foot-long and 15-feet-high wall continues to attract visitors.