Naturally formed by two 300-foot sandstone monoliths and sitting at 6,450 feet above sea level, Red Rocks was here long before anyone thought to put a stage in it. The acoustics are an accident of geology. The sunsets are not an accident of anything — they just happen like that every night. Bands have been making pilgrimage here for a century: U2 filmed here, Phish has played here more times than most venues have hosted any act, and the audience always leaves wondering why every concert isn't held outdoors in the mountains. Denver International is 45 minutes east. The altitude hits before the first song ends.