Lava Beds takes a while to grow on you. It’s a seemingly desolate place with high plateaus, cinder cones, and hills covered with lava cinders, sagebrush, and twisted junipers. Miles of land just like it cover most of this corner of California. So why, asks the first-time visitor, is this a national monument? The answer lies underground.

The earth here is like Swiss cheese, so porous in places that it actually makes a hollow sound. When lava pours from a shield volcano, it doesn’t cool all at once; the outer edges cool first and the core keeps flowing, forming underground tunnels like a giant pipeline system

More than 330 lava-tube caves lace the earth at Lava Beds -- caves open to the public to explore on their own or with park rangers. Whereas most caves fuel visitors’ fear of getting lost within their huge chambers, multiple entrances, and bizarre topography, these tunnels are simple and relatively easy to follow. Once inside, you’ll feel that this would be a great place for a game of hide-and-seek.

Call the Lava Beds National Monument (530/667-8100; www.nps.gov/labe) for information on ranger-led hikes, cave trips, and campfire programs. The visitor center is at the southern end of the park. The entry fee is $10 per vehicle for 7 days, $5 per bike or walk-in, and $10 a day for camping.

Park elevations range from 4,000 to 5,700 feet, and this part of California can get cold any time of year. Summer is the best time to visit, with average temperatures in the 70s Fahrenheit; winter temperatures plunge down to about 40 degrees Fahrenheit in the day and as low as 20 degrees Fahrenheit by night. Summer is also the best time to participate in ranger-led hikes, cave trips, and campfire programs.