So when I came across the Philadelphia Grotto, a group dedicated to the exploration of caves, I had little desire to slither around in the nether regions of God's green earth. With so much to do topside with the holy sun as witness, why would someone want to crawl around so far removed from fresh air, sunlight and medical aid? So naturally, I called Hans Nagl.

A LAND DOWN UNDER: Our reporter (left) and Hans Nagl make their way to the "popcorn room."

Nagl is the chairperson of Philadelphia Grotto, a group chartered in 1947 as a member of the National Speleological Society and one of the most active caving clubs in the United States, counting 80 members culled from Philly and its outlying areas. He's a jovial man — 6-foot-plus and overflowing with energy. With little hesitation Hans invited me to explore a limestone cave in central Pennsylvania.

As a mild claustrophobe, I was wary of crawling around on my stomach, but Hans brushed away my concern. "I took my 12-year-old son there and he also made it," says Nagl. This didn't make me feel any better.

On a clear, sunny Saturday morning a group of 12 cavers gathered on a lush green hillside on the outskirts of a rural Pennsylvania town called McCallisterville. We put on hiking boots, kneepads, helmets and jumpsuits that make us look like a motley crew of mechanics, astronauts and hazmat workers. Atop our noggins we attach our visual lifelines — battery-powered headlamps.

At 11:30 a.m., a group of two women and 10 men, varying in levels of experience and ranging in age from 14 to 56, stood ready to take the plunge. I am the only one who has never tested his subterranean nerves, and up to the last second I stand in disbelief, staring at a metal chute 2 feet in diameter that juts from the ground. Worse yet, once we're below the surface, the cave will be locked from the inside so no one can follow us in. This seems to be a bad idea.

Grotto member Allen Maddox explains that our goal is to do as little damage to the cave as possible. Don't knock any formations loose. Don't leave any trash. And don't emit any waste in the cave because it and the smell would linger for a long, long time.

Though my suddenly quivering bowels disagree, this makes sense. Along with exploration and mapping, the Grotto aims for preservation. Cave access to the general public is limited — both to protect the cave itself and the weekend-warrior explorers who might put themselves at risk, leading to costly, time-consuming rescues. In fact, the common name "spelunker" is actually a derogatory term within the community used to describe a less serious approach to what the Grotto considers a scientific pursuit. (Bumper stickers and T-shirts popular among cavers read: "Cavers rescue spelunkers.")

"People wanna make table ornaments out of [stalactites and stalagmites] and that's really dumb," says Nagl, explaining that delicate formations that take thousands of years to develop deserve more reverence. "Cave Softly" is the group's motto.

However, what I'm more worried about is being paralyzed by fear as soon as I go down. Nagl and Maddox promise that the small dark hole opens up into a big room once you go down a bit. I'm skeptical, but I slide down the 10-foot-long pipe anyway. I can hear my heart pounding.

There's that musty, earthy smell that I expected. And it's dark. I scramble down a gravel pitch and watch the headlamps below continue to descend. Suddenly the ceiling rises 30 feet and a cavernous room materializes from the shadows. The limestone walls and boulders are a dull, grayish brown. Only the bright spotlights gleaming in the dark are visible. The only sound is the rustling of gravel as it tumbles down. And the air is not musty or earthy anymore. It's a cool, moist, refreshing 50 degrees.

We split into two groups. One goes through a tight, knee-high squeeze called the "rabbit hole"; my group heads onward. Thank God. There's no way I'm going through there.

Nagl, Maddox and Amos Mincin lead. This first "trunk" of the cave is easy going at first. Like hiking a rocky stream bed, it requires the agility to navigate tight squeezes and scramble over boulders. The damp rocks are covered with a film of mud — I imagine it's a little like rock climbing with peanut butter on your fingers.

Fossil remains of coral and other sea creatures texture the walls and ceiling — evidence that Pennsylvania was below the ocean millions of years ago.

"What if there's an earthquake?" I think to myself. "I'll die here."

Nagl reminds me that if you let the anxiety take over, you literally experience tunnel vision and miss the beauty of the cave.

We enter the "sculpture room," where nearly a hundred handmade sculptures have been fashioned by some inspired cavers from the muddy sediment on the cave floor — little people, a hand, a mushroom. They look ancient and peaceful in such isolation. And before we leave this part of the cave, I end up crawling on my stomach to get through to the "popcorn room," which has some of the most intricate and untouched formations.

We return to the cavernous room, approaching the rabbit hole. Without hesitation, I slide through the tiny opening, on my back, feet first.

For Nagl, caves are among the last unexplored places on earth. "If you go into a room where no human has been before, it's really an awesome experience. You see things that no eye has seen before."

We begin the most physically challenging part of the expedition, which requires shimmying along the "chimney" — a 40-foot-long crevice that drops 20 feet below. With our backs against one side and our feet propped against the opposing wall, we make like human wedges. The difficulty of this stretch could be measured in man-grunts as we slowly slide horizontally, trying not to look down.

Frustrations are tempered by Nagl's impromptu "Hi ho, hi ho, it's off to work we go." The grimaces, tired legs and muscle strains are all part of the game. As we go deeper and deeper, with the passages narrowing like plaque-filled arteries, I eventually have to call it quits. Three hundred and fifty feet in and 140 feet below the surface, I let them know that I've had my fill. "If you're really scared and don't want to do something, we'll take you out of the cave," Nagl had assured me earlier, and I now take him up on that offer.

The trip back up goes smoothly. Four hours after it was locked, we unlock the gate and I thrust myself toward the light, like a mammal through the birth canal.

For me, being totally enclosed in the earth's rocky womb provided an adrenalin-infused after-buzz that would last for days. Nagl took the trip in stride: "There's nothing better than a beer after a caving trip," he says, topside, as he passes me a Yuengling Black & Tan. Perhaps I got in a little too deep.

(d_wilson@citypaper.net)