There are plenty of reasons to visit Colorado this fall, and pretty mountain scenery won't be the main attraction come September. Denver's Monolith Festival, which debuted last year, will see its second installment take place Saturday, September 13 and Sunday, September 14 at the Red Rocks Amphitheater, and a boatload of names are slated for the bill, including Atmosphere, Hercules & Love Affair (pictured above), Cut Copy, CSS, and more.