AKERS, Mo. — The open gate, unlocked after more than three decades, represented fulfillment of a boyhood dream and a tribute to a pioneer in Missouri cave science.

Wet-suited and rope-rigged, Tony Schmitt stepped through the gate and rappelled 90 feet through darkness, alighting at his inflated raft. It floated in a subterranean lake nearly the size of a football field.

With his descent, the veteran caver became the first explorer since 1971 known to have entered the huge dome-shaped cave under Devil's Well. The well, a natural wonder in Shannon County owned by the National Park Service, is a steep, funnel-shaped sinkhole almost hidden by towering trees.

At the sinkhole's lowest point is the cave opening, a sheer drop. A small waterfall trickles from a mossy rock face and cascades into the lake below, sending up mist and eerie echoes, the St. Louis Post-Dispatch ( ) reported.

Despite its remote and winding gravel access, nearly every day of the year a handful of visitors find their way to Devil's Well. In summer, they'll traipse down a staircase that winds through lush undergrowth and dappled sunlight.

The air cools as one passes under an arched natural bridge and enters a platform overlooking the hole. Eyes adjust to the gloom as one peers through the metal bars of a sturdy vertical gate. A motion detector trips a switch and a bright light illuminates the vertical pit and the water below.

"Wow" is the typical response.

Schmitt first visited Devil's Well at age 10 as a Boy Scout. "I immediately wanted to go in, and I've wanted to ever since," he said. It was "one of the caves that sparked my interest in caving."

Thirty years and countless caves later, Schmitt, of Fenton, is now an experienced cave surveyor and proficient in single rope technique, a method of ascending and descending cliffs and cave openings.

That method did not exist in the mid-1950s when explorers first entered Devil's Well. Back then, landowner Bill Wallace installed a wire cable attached to a bosun's chair, which was raised and lowered with a hand-crank winch, a trip that took 15 minutes each way.

The Park Service purchased the Devil's Well property in 1974, and it became part of the Ozark National Scenic Riverways. The winch apparatus, considered unsafe, was removed. By 1980 the present viewing platform and gate were completed. No one was allowed beyond the gate.

Thousands of visitors have wondered what is below. "How can you approach that hole and not be stricken with curiosity?" said team member Dan Lamping, of Affton, president of the Missouri Speleological Survey.

Curiosity prevailed, and about a year ago, the National Park Service approved a proposal from the Cave Research Foundation for a new entry. For 20 years, this foundation has helped manage and monitor Riverways caves parkwide, said Ozark director Scott House.

Why so long between entries? In the past, the Park Service didn't have the expertise to safely enter Devil's Well, said spokeswoman Dena Matteson. "This venture became a possibility," she said, when the Cave Research Foundation assembled a team proficient in single rope technique.

A new chapter for Devil's Well began June 25 as Schmitt rappelled downward. He could barely see through the rivulets dripping off his helmet. Illumination from above almost disappeared as he left the upper tube-like passage and entered the yawning black dome above the lake. At the bottom, waterfall noise became a chaotic echoing crescendo.

Five cavers descended, each with specific missions. Lamping and Bob Lerch, of Columbia, Missouri, took photos. Schmitt scouted the lake's perimeter.

Mike Tennant of Brentwood and Joe Sikorski of Lemay searched for cave life. They saw a turtle and frogs, but no fish, due to poor visibility caused by recent rain. Historically, the lake has been home to blind cavefish and cave crayfish.

Team members were surprised to find remains from previous explorations, a wooden platform built in the mouth of a muddy cave passage. It held a decades-old joke: a clipboard marked with the word "help."

Topside support team Mark Andrich of Ballwin and Rick Haley of St. Charles hauled up gear. They were equipped for emergencies, but all went as planned.

House said he anticipates future entries, which might yield maps of additional passageways and continued search for cave species.

The outcome pleased the Park Service. "We are excited about the possibility of future monitoring trips," Matteson said.

Early on exploration day, a thin man of 80 years watched from an upper platform as team members deployed.

He was Jerry Vineyard, a legendary figure in the eyes of Missouri cavers and one of Schmitt's personal heroes.

Vineyard had participated in early Devil's Well expeditions starting in 1956, the same year he co-founded the Missouri Speleological Survey. He is known for mapping numerous caves, for serving as the Missouri state geologist, and for writing "Springs of Missouri."

Particularly valuable to the exploration team is Vineyard's 1963 University of Missouri master's thesis. It provides baseline data into the extensive Devil's Well system, which includes side branches and a water-filled tube that connects to a smaller subterranean lake.

Using dye, Vineyard proved in 1961 that water from Devil's Well emerges a mile away at Cave Spring on the Current River, a popular stop for floaters. He measured the 20 million-gallon subterranean lake at 400 feet long, 100 feet wide, and up to about 100 feet deep.

Vineyard vividly remembers his first entry into Devil's Well, "an absolutely overwhelming experience." And so it will be for those to come.

"It hasn't lost any of its excitement or attraction, or its terror. It's a very scary place to be," Vineyard said.

That Vineyard, of Ozark, Missouri, traveled on June 25 to pass the torch to the next generation of Devil's Well explorers "was huge. It was emotional," said Schmitt. "It was a tip of the hat to his generation of cavers."