A colossal marble cavern, Lehman Caves features a staggering collection of formations including stalactites, stalagmites, helictites, flowstone, popcorn and more than 300 rare shields. They are a fragile resource: the only way to view them is by guided tour, either the 60-minute Lodge Tour (adult/child $9/5) or the slightly more demanding 90-minute Grand Palace Tour (adult/child $11/6), which takes in the remarkable Parachute Shield. Advance reservations are required, but you can try your luck on the day. Book tours via the reservations hotline – or at the Lehman Caves Visitor Center, the access point for the caves. The temperature inside the caves is a constant 50°F (10°C); bring a sweater.