Farmer Lester Howe graciously credited his cow Millicent with the 1842 discovery of this passage to New York's underworld. Inspired by Kentucky's considerably larger Mammoth Cave, Howe began the business of guiding curious visitors down to the cavern, but things didn't really take off until the installation of lighting and walkways in 1929. Today you can't miss the ads on billboards for miles around; Howe Caverns comes in second only to Niagara Falls for the state's top natural attraction. A bit more manageable than Lester's original 10-hour tours, the 80-minute guided visit includes a quarter-mile ride on the underground Lake of Venus.