The Bubblegum Alley could pass as the dirtiest alley in the world. But, even if a lot of people find it disgusting and unsanitary, it has survived several clean-up attempts. It still stands today as the most talked about landmark and continues to draw a lot of visitors from all over. This 15 feet high and 70 feet long walls are located downtown of San Luis Obispo (SLO) in California. It became popular because of the thousands of chewed bubble gum stuck on its walls. It is believed that students of SLO High School and Cal Poly students started this in the late 1950s. This local landmark changes from time to time as more people (locals, students, tourists and artists alike) come to stick their gum and make their own mark on its walls.