Head south now to spend the night at Mammoth Cave National Park, site of the longest cave in the world. Though about 330 miles of passageways have been found, more of the cave is yet to be explored. Begin tomorrow with a tour.

Details

From Lexington to Bardstown, take the Bluegrass Parkway. Then follow a series of well-marked back roads to Loretto, Hodgenville, and Cave City. A state road map will keep you from getting lost. Stay in the park at the 42-room Mammoth Cave Hotel (270/758-2225), $49 to $75. A nearby alternate in Cave City is the 110-room Days Inn (270/773-2151), $70. Dine at the Mammoth Cave Hotel. The fried-chicken plate (salad, vegetables, biscuits), $9.95. Further information (800/346-8908, www.cavecity.com).

Day 3: Adventureland

Mammoth Cave to Cumberland Falls, 115 miles. This is a day for adventure. Or simply enjoy the beauty of two natural wonders.

If it's challenge you seek, sign up for one of Mammoth Cave's more strenuous tours. Popular with the hardy is the two-hour trek into the underground to view Frozen Niagara ($9), where fluted stalactites spill from above like a large pink waterfall. You will have to negotiate 300 steps, shuffling single file, ducking, and dodging down a tight, twisted path and steep stairway. Don't bump your head in the dim light. The rest of you can get a glimpse of the spectacle on the gentler 30-minute Discovery Tour ($4). Reservations are necessary (800/967-2283 or http://reservations.nps.gov).

Afterward, spend the afternoon hiking, horseback riding, swimming, or relaxing by the river at Cumberland Falls State Resort Park. Only riding involves a fee-$12 for 45 minutes. Horse and foot trails snake through shady Appalachian woodlands, dipping and climbing much of the way.

Cumberland Falls, a 60-foot drop of the Cumberland River, looks like a smaller version of Niagara , and its roar is similarly thunderous. Below the falls, Sheltowee Trace Outfitters (800/541-7238, www.ky-rafting.com) runs all-day rafting trips ($53.25). Spend another day in the park and join in the fun.

Details

From Mammoth Cave, take I-65 south to the Cumberland Parkway east. At Somerset, take U.S. 27 south to Kentucky Route 90 east to Cumberland Falls. Stay at the park's 52-room Dupont Lodge (800/325-0063), $73 for a one-bedroom cottage in the woods. An alternate in Somerset is the 54-room Days Inn (606/678-2052), $55 weekdays, $60 weekend. Dine at the park's cafeteria, all-you-can-eat for $11.95.

Day 4: An American sampler

Cumberland Falls via Berea and Harrodsburg to Lexington, 105 miles. Ahead awaits beautiful mountain and pastoral scenery, highlighted with a bit of offbeat shopping and stops at two worthy historical sites. It's a day as American as apple pie.