Culture of San Luis Obispo

Lots of mystery surrounds the "underground city", or the series of tunnels that exists beneath the city.

One of the largest Mardi Gras parades west of the Mississippi was held in San Luis Obispo, but canceled in 2005 because of difficulties related to crowd control and alcohol consumption.

Cal Poly's open house, Poly Royal, was held annually from 1933 to 1990. It was canceled in 1945 due to war rationing. It began as a show-and-tell for students to display their projects. It traces its origins to the 1904 Farmer's Institute and Picnic Basket. By the 1980s, as the college became "the most popular...university in the 19-campus CSU system", Poly Royal began drawing over 100,000 people from throughout the state, including 126,000 people in 1985. Concerts, parties, and other entertainment were added and it earned $3–4 million in revenue for the city every year.

Following a "mini-riot" in 1989 at an off-campus apartment during Poly Royal, the events in 1990 would cancel the event "indefinitely." Two nights of rioting on April 28–29 led to 127 arrests, over 100 injuries and 14 police injuries on top of "several hundred thousand dollars'" worth of damage. A liquor store near campus, Campus Bottle, was destroyed by revelers demanding alcohol. The second night was much larger than the first as people were leaving a concert on campus and parties off-campus were broken up and revelers flooded the streets. Mayor Dunin called the events "the worst experience in the history of San Luis Obispo." After a meeting between Mayor Dunin and University President Warren Baker the