STRANGE AS IT may seem in sunny California, numbering among the state's most amazing parks is one where you can't fully appreciate the scenery in broad daylight. The park is Lava Beds National Monument, located just south of the Oregon border near the town of Tulelake, and the area's strange rocky surface masks an underground playground of more than 500 known lava tubes, formed by rapid cooling around molten lava streams.

Open to exploration with the help of a bump hat and flashlight, many of the tubes at Lava Beds are an estimated 30,000 years old, and they contain a fascinating mix of both ancient and 19th-century history whose marks are often imperceptible from above ground. With the highest concentration of lava beds in North America, the park is also a hands-on crash course in the mechanics of volcanism.

Cave Loop Road contains a dozen easily accessible caves that reveal exquisite variations of texture and color. Floors might be smooth, decorated with stalagmite drips, or awash in ropy rock flow. Some caverns ooze with trapped moisture; a few enclose glassy floors of ice. As your flashlight beam lights up the walls, a spectacular array of bright reds, rich blues, and sparkly golds materializes.

Although most of the caves register no discernible light after the first bend, a few shallow tubes have cracks exposing ethereal strands of sunlight. Beyond the reaches of daylight, however, the utter darkness of the tubes envelops a visitor, and without another source of light, the thick, cold void can feel oddly protective or deeply unsettling, depending on your state of mind.

Lava tube dimensions vary from caverns of 60 feet in diameter to squeeze-through passageways that give shape to claustrophobia. Long, profuse tunnels branch out and snake around, with subsequent tubes often stacked on older ones – the spelunking possibilities go on forever. Muffled sounds reverberate abnormally, bewildering the ears and making it easy to lose track of someone just ahead or behind. At last count, the labyrinthine caves total a combined length of just more than 28 miles, with Catacombs, the longest single cave, measuring a whopping 6,903 feet. If the idea of getting lost in deep underground tunnels makes you a tad nervous, buy a detailed cave map at the visitor center.

The subterranean passageways also bear witness to one of the last major battles between a Native American tribe and the U.S. government. With the arrival of white settlers in the 1850s, the Modoc tribe struggled to remain on the valuable lakeside land of its ancestral home, and in 1872 tribe members refused a forced resettlement. During a fierce battle ('72 to '73) with the U.S. Army, a group of 50 Modoc fighters and their families used their knowledge of the lava beds to hold off the troops for almost six months, as the army contingent gradually increased to 20 times the size of the Modoc resisters. Led by a warrior named Kintpuash (also known as Captain Jack), the Modocs used natural trenches within the lava hills as a fortress complex. The U.S. military finally prevailed, however, capturing and hanging a number of Modoc leaders and imprisoning two on Alcatraz. The remaining group was sent to a reservation in Oklahoma, where about 200 descendants live today.

Although the most fascinating portions of the park lie beneath one's feet, there's plenty worth investigating on the earth's surface as well. A short but steep hike up the cinder cone to the Schonchin Butte fire lookout offers a comprehensive view of the area's convulsive geological past. Lava flows spread out in three directions, and low dark mounds of rock created by spatter vents testify to the dramatic volcanic activity that shaped the terrain. After scanning the defensive topography that sheltered the Modocs in the area now called Captain Jack's Stronghold, a visitor should pause to read the interpretive plaques marking other significant Modoc War sites that dot the region.

Near Tule Lake, Petroglyph Point showcases cultural artifacts from yet another epoch in the history of the land. Petroglyphs are prehistoric carvings or drawings made on soft rock surfaces, and curiously high on the cliff side are thousands of these ancient graffiti characters. Although Tule Lake was significantly drained for farmland use in the 1920s, its shores once extended much farther, its waves lapping up against the side of this volcanic vent. Early inhabitants of the region paddled out on the lake to fashion intricate figures in the volcanic tuff. The cracks and bubbles in the slowly eroding cliff now form nesting areas and shelter birds such as barn owls and cliff swallows.

Lava Beds is rarely crowded, and you can often wander through its caves without seeing (or more likely, hearing) another soul. And although the tribe was ultimately unsuccessful, the Modoc resistance makes the park a vibrant primer in both political and geological history and a sobering reminder of California's pioneering past.

If you go

Getting there Lava Beds National Monument sits just south of the California-Oregon border near the town of Tulelake, and admission is $10 a vehicle. www.nps.gov/labe.

Staying there Open year-round, Indian Wells campground is the only lodging in the park. Sites are $10 a night and are available on a first-come, first-served basis. Go to the park Web site and click on Plan Your Visit or call (530) 667-2282, ext. 232.

What to wear For lava tube exploration bring warm clothes, sturdy shoes, a strong flashlight, and a hard hat or bike helmet for bump protection against low ceilings.

Reading material For a detailed history of the Modoc War, read the chapter "The Ordeal of Captain Jack" in Bury My Heart at Wounded Knee (1970), by Dee Brown.