In carbonate caves such as California Caverns, calcite deposits take many shapes besides the familiar stalactites and stalagmites. There’s "bacon," curving formations striated with darker mineral deposits, exactly like a thick slice of breakfast meat suspended from the roof; delicate sprays of beaded helictites, glittering like cave tinsel; and "soda straws," hollow tubes of calcite bristling like porcupine quills on the stone ceilings. "The archways and ceilings were everywhere hung with down-growing crystals," John Muir noted, "like inverted groves of leafless saplings, some of them large, others delicately attenuated, each tipped with a single drop of water like the terminal bud of a pine tree."

We scramble beneath these formations to a series of chambers that explain the "Cave City" moniker. By the end of the 1850s, a city had sprung up around Captain Taylor’s discovery. During the heat of summer, the caves became a extension of the town. The first chamber we enter is covered with graffiti dating back to 1853. Just as prehistoric cave visitors left handprints to mark their presence, modern humans seem to enjoy scratching their names into the rock. Art shows us Masonic symbols and the names of once-famous citizens and whole families, each giving a tangible clue to the past. Thinking that Muir resisted carving his initials in a cave, I suppress my own temptation to do so. The urge to leave one’s mark may be visceral, but it’s destructive to such a fragile environment.

We walk deeper into the mountain along trails coated with sticky mud. The noise of our movements, breathing and voices cut through the caged silence of the tunnels. Mud sucks the soles of our shoes. Enveloped in the deep, moist odor of wet earth and still air, we grope along the path until we meet the cheerful incandescent glow of the Trail of Lights and arrive at the mouth of the Womb Room.
"This is our claustrophobia test," Art announces, grinning, pointing to a narrow aperture in the rock. "If you can stand to be in here, you’ll make it through the most enclosed places on our tour." With that, he makes like Alice’s rabbit and dives in headfirst. We peer after him into an opening barely the width of a grown man’s shoulders. Tentatively, we follow feet first and find ourselves in a small, round "room." By tucking into fetal position, we’re all able to fit. Art swears he once shoved an entire Boy Scout troop in here, but it’s a tight squeeze for the seven of us. Getting out again is a greater challenge, for the rock is smooth and slippery. Art shoves from the bottom while a helpful tourist above pulls on my arms. Only by abandoning all dignity am I able to finally lurch through and roll, limbs flailing like an overturned sow bug’s, into the brightness of the Trail of Lights. A group of tourists breaks into applause.

In the absence of light, Art says, the human brain labors to create a semblance of ordinary reality. Seated in another chamber after exiting the Womb Room, we turn off our headlamps. Darkness descends like an inky curtain. Art explains that in such settings cavers will "see" auras of human shapes, or even detailed visions in the dark, as the mind strains toward the familiar. When we snap on our lights again, the unconscious urge to find the ordinary remains. I’m certain that’s what motivated the good folk of Cave City to transform the

calcite rooms into extensions of their above-ground habitat. Civic meetings were held in one chamber shaped like a natural amphitheater, and another was used for concerts. In the "chapel," parishioners swore they saw the face of a bishop in the calcite droppings gathered around a boulder "pulpit," and calcite crosses apparently ringed the chamber as well. Elsewhere, weddings were held around a massive mound of pearly calcite resembling a bridal gown.

Moving on, we pass a lake so still it resembles a mirror, perhaps the same one Muir meant when he wrote of "a charming little lakelet of unknown depth, never yet stirred by a breeze. . . ." The reflection of the calcite-studded ceiling on its surface plays an optical trick, making us think the floor of this chamber is studded with calcite barbs, exactly like a bed of nails—Art’s nickname for the spot.

The centerpiece of these caves is a room Muir never saw. It was discovered in 1962 when legendary caver Tom Haley squeezed through an eight-inch slot into the "Jungle Room." Com-pletely encrusted with twisting calcite formations, it is a caver’s pot of gold—a fantastic landscape that could only be found beneath the floor of the earth. We gape at the starkly-lit scene. The floor seems to boil in calcite waves. All around, the luminous stuff forms semi-recognizable objects the way clouds melt and merge into a semblance of animals and land masses. Casting a flashlight around the bejeweled room, Art points out the shapes of a meditating Buddha and a tiered temple. More vernacularly, he also indicates a "Playboy pinup," a snail and a snake. Here are fairy alcoves, complete with "crystal decorations" even more breathtaking than the "splendor in the darkness" of Muir’s memoir. We are thrilled by what we’ve seen, and tired, but our expedition isn’t over. Art is about to introduce us to the more secretive side of the cave.

Until now, our adventure has been strenuous, but not scary. We will begin the next part of the visit by rappelling down an 80-foot chute deeper into the earth. For an experienced caver, such an endeavor is as easy as sneezing. For a bunch of fairly sedentary, mostly middle-aged museum types, it’s akin to bungee-jumping into the Grand Canyon. We walk back to the staging area to outfit ourselves with harnesses, each of us trying to recall why caving had seemed such a great idea the week before, and trying to remember exactly how we feel about heights.

Some of us remember all too well as we stand staring into a hole in the ground that marks the beginning of California Caverns’ "Downstream Circuit." We’re supposed to fasten our harnesses to a rope and lower ourselves through this slot into a wet pit. Some of us opt to decline. I don’t like dark places, wet places or very small constricting spaces, yet now I’m asking myself to confront all three. I study the nervous expressions of my fellow adventurers as they disappear down the chute, and try to objectify the experience by thinking about the mythology surrounding our relationship to the earth’s depths. None of that is much comfort, for the stories are grim: Tom Sawyer and Becky Thatcher lost in a cave Mark Twain may have patterned after California Caverns; Bilbo Baggins fighting for his life in a riddle contest with the slimy Golum; Persephone kidnapped by Hades, borne away to the darkness of the underworld.

When my turn comes I steel myself, putting aside visions of smashing my brains against the rock, trying not to think about losing my grip and sliding a hundred feet to my doom, or being impaled on the vicious shard that surely awaits me at the bottom. I take a breath and grab the rope, half-sliding, half-bouncing down the rock. Rather than a vicious shard, what greets me is a round of applause. I feel a flush of pride. We’ve done it—conquered our demons.

Next, we perch on a huge boulder by a glassy lake waiting our turns to rappel down a sheer rock face to the water, then shuttle across in an inflatable raft. I glimpse massive chunks of rock rising like the walls of a cathedral hundreds of feet above our heads, some of it arrested in mid-slide during some ancient tectonic shudder. Asked to turn off our headlamps to conserve batteries, we sit quietly in the dark listening to the soft paddle of oars as the raft approaches. One by one, my companions disappear until I am alone with the guide and my nerves.

There are scientists who believe that humans are born without instincts, but I’m sure they have never had to rappel backwards down a 40-foot boulder in complete darkness. If they had, they would know that this feat runs contrary to everything your body and mind consider reasonable. I’m asked to grab hold of what appears to be a flimsy rope looped around a corner of rock that couldn’t possibly support the weight of a fly, brace my feet against a sheer cliff face, hang my butt over a bottomless void and jump backwards into pitch-black deep space. This is impossible, at least for the few minutes that I stand at the edge ignoring Art’s encouragement while my instincts scream: Nooooo! I lean back. I jump. I realize that lunacy descends in that fragile moment when you break through the conventional barriers your mind creates to protect you from danger, and that in going against everything that makes sense, I am now completely crazy. I feel great. My feet spring against the rock all the way down. I am unafraid. I am Spiderman!

continued...