4. Merriweather Post Pavilion, Columbia, Maryland
Designed by architect Frank Gehry, known for shapes that seem structurally impossible, this outdoor theater is a huge wooden slab that seems to float over a hillside near Baltimore. Since opening in 1967, it's hosted everyone from Phish to Led Zeppelin – and in 2009, it gained a new kind of fame when Animal Collective, who grew up in Baltimore, named their latest album Merriweather Post Pavilion. (There's a reason no band has ever named an album after the 1-800-ASK-GARY Amphitheatre.) The venue is flexible enough to go big or small with ease. "It feels great whether there are 6,000 or 16,000 people there," says Fall Out Boy manager Bob McLynn.
Fun Fact: The venue is named after cereal magnate Marjorie Merriweather Post, an early patron.