Beneath the area's rumpled hills, eons of dripping and flowing waters have worn through the limestone bedrock, creating a maze of underground rooms, rivers and sinkholes. Nearby Mammoth Cave National Park preserves the world's largest known cave system. Sign on for a tour for an introduction to this geological wonder. If you're up for adventure, try the belly-crawling six-hour Wild Cave Tour. Cleanup is easy at KOA, where you'll find hot showers and laundry facilities. Camping Cabins, shady pull thrus, a swimming pool, mini golf and a playground for the kids make this a relaxing base. In fall, the trees will reward you with glorious color.