MONTANA

Lewis & Clark Caverns State Park near Three Forks (406-287-3541). If you think of caves as creepy holes in the ground, this park will change your mind. Tours ($10 for adults, $5 for kids 6-11 and kids under 6 are free) take you past otherworldly formations, from the 32-foot-high Empire State Column to the Popcorn Room, covered in tiny white clusterites. Bunk down in one of 44 campsites or three log cabins.

IOWA

Maquoketa Caves State Park in Maquoketa (563-652-5833). Thousands of years ago, Maquoketa's caves were home to early man. Today, more than 13 are open for exploration, including Steel Gate Passage, an 800-foot stretch where the brave can experience total darkness. Spend the night above ground at one of the 29 campsites.

MINNESOTA

Forestville State Park/Mystery Cave in Wykoff (507-352-5111). Minnesota's largest cave and an 1899 boomtown are paired in this unusual 2,400-acre park. Cave tours are $7 for ages 13 and older and $5 for ages 5-12. Kids 4 and under are free. Escape underground to stroll on catwalks or investigate the blue water of Mystery Cave's Turquoise Lake. Later, talk to the characters who work in the town's bakery or distillery, then spend the night in one of the 153 campsites.

Please keep in mind that phone numbers, addresses, and prices are subject to change. Originally published in June 1996. Updated April 2004.