About the wonder

Name: Craters of the Moon National Monument and Preserve.

Location: About 183 miles east of Boise and 18 miles southwest of Arco.

Size: 750,000 acres.

What to see: Volcanic formations created by 65 flows of lava between 15,000 and 2,100 years ago. Formations include lava tubes, cinder cones and spatter cones.

How to see it: Seven-mile loop road takes motorists past some of the most striking features.Operating hours/season: Craters is always open. The loop is closed to vehicles from mid-November to mid-April. Call or check Crater’s Web site before you go.

Fees and reservations: Admission is $8 per vehicle or $4 for people who walk in; young people under 16 pay nothing. Fee will increase to $10 per vehicle and $5 per walk-in beginning in mid-April.

Accessibility: Two trails are handicapped-accessible. So are a campsite, bathroom and the visitors center.History: Calvin Coolidge named Craters of the Moon a national monument in 1924. Original monument of 54,000 acres was expanded to 750,000 acres in 2000.

For more information: Call 208-527-3257; visit Crater’s Web site at http://www.nps.gov/crmo/index.htm

Biggest surprise: In this nearly waterless landscape with practically no soil, look for tiny lush green ferns that grow in cracks in the lava rocks.

Floating rock: A number of huge rocks — once part of a cinder cone — were floated by lava for a couple of miles and dropped in a field now called Devil’s Orchard. Craters’ staff nicknamed one of the largest of these rocks “warehouse block.”

Coolest Craters critter: The pika, a relative of the rabbit. The Craters’ species is isolated by volcanic terrain from pikas elsewhere in Idaho. Pikas can’t take heat much above 85 degrees. When Crater’s lava heats up — well over 100 degrees — pikas burrow in cool holes in the lava until night, when they come out and feed. Park officials wonder how global warming will affect the pikas.

The wonder of the wonder: Spatter cones. Little volcanos in which visitors can walk give a sense of what it was like during the eruption 2,000 years ago.

Volcanic lunch: Pickle’s Place in nearby Arco serves the Crater Burger, created by owner John Danz. It consists of hamburger and sauteed onions and mushrooms, topped with black olives that represent the dark-colored lava.