Cameron Cave offers a different underground adventure; you tour the cave by lantern light, seeing it as it was when first discovered. The only changes made were those necessary to make the tour more comfortable and to meet Missouri State Safety regulations for show caves. A guided, 90-minute tour takes you through this unique, complex-maze cave. Cameron Cave (discovered in 1925) is on the property of the Mark Twain Cave; one mile south of Hannibal on Route 79. New: Total Eclipse Tour, $32 reservations only, 4-10 people per tour. Open two weekends before Memorial Day to a few weekends after Labor Day.