Watch day turn to night as you descend into the dark depths of Mark Twain Cave. Equipped with a reliable flashlight and a sense of adventure, there's no saying what you might discover down there.
To visit this natural underground attraction, you'll need to find your way to Hannibal. There are plenty of other worthwhile attractions in this area, including Mark Twain Boyhood Home and Museum, Mark Twain Cave and Cameron Cave, and Mark Twain Memorial Lighthouse.