There's something fundamentally mysterious about caves and tunnels. Maybe it's their darkness or the fact that they open into the very body of the Earth. They are invariably the subjects of adolescent adventure stories, such as the Hardy Boys, Nancy Drew mysteries, and R.L. Stine's books. And they serve as backgrounds in exciting stories directed at older audiences as well, such as Jules Verne's A "Journey to the Center of the Earth" and the Indiana Jones films. Tunnels represent the unknown and touch the fears that reside deep in the primitive human subconscious.

People who claim to have first- or second-hand knowledge or experience with these tunnels make many astonishing claims: that they contain long-lost cities; that they are inhabited by advanced civilizations — perhaps the descendants of Atlantis; that they are bases for extraterrestrials and their flying saucers; that they are bases for secret government installations. The government no doubt has top-secret military installations deep within mountains and perhaps underground, but this, of course, is the least fantastic of the stories.

Here are highlights of some of the more extraordinary claims. Since these stories come without photos or any other kind of verification, consider them skeptically. In any case, they are fascinating.

Grand Canyon Mystery

The April 5, 1909 edition of The Phoenix Gazette carried a story entitled "Explorations in Grand Canyon." According to the article, a man named G.E. Kinkaid made an astonishing discovery while on an expedition, sponsored by the Smithsonian Institute, in the Grand Canyon. Among his findings:

A mammoth chamber about 1,480 feet underground from which radiates dozens of passageways "like the spokes of a wheel."

Several hundred rooms, some of which contain artifacts such as weapons and copper instruments of a kind that have never been known to be native to the Americas.

A crypt containing mummies—all adult males wrapped in a bark fabric.

A shrine containing a Buddha-like idol sitting cross-legged with a lotus flower in each hand.

Stone tablets on which are carved mysterious Egyptian-like hieroglyphics.

The article also mentions a legend of the Hopi Indians that says their ancestors once lived in an underworld in the Grand Canyon.

Crump Burial Cave

In 1892, Frank Burns of the U.S. Geological Survey reported that he found strange coffins in the Crump Cave along the southern branch of the Warrior River in Murphy's Valley, Alabama. The wooden coffins appeared to be hollowed out by fire, then chiseled with stone or copper tools. Each coffin was 7.5 feet long, 14 to 18 inches wide, and 6 to 7 inches deep. The lids were open on each empty coffin. The specimens were sent to the Smithsonian, which suggested the coffins might actually be troughs. In any case, the museum lost the artifacts.

Tunnel Network Under California

According to an article entitled "California Floats on Ocean?" in the Fall 1985 edition of Search magazine, a high-ranking but unnamed Naval officer told of the discovery of a huge network of tunnels under portions of the West Coast of the U.S. He said that U.S. nuclear submarines had explored some of these tunnels, which are accessible just off the continental shelf, and had followed them inland for several hundred miles. Here are more highlights of this incredible claim:

What is being passed off as the San Andreas Fault are actually large, unsupported chambers that are in the process of collapsing.

A well-known U.S. nuclear submarine lost its way in one of the passages and was never heard from again. (Two U.S. nuclear submarines have disappeared under mysterious circumstances — the U.S.S. Thresher and the U.S.S. Scorpion.)

Some of California is actually floating on the ocean. When oil companies began pumping oil from beneath the city of Long Beach, it began to sink — up to 26 feet before the pumping was stopped.

More and More Tunnels

A couple from Bishop, California discovered a circular hole in the ground while exploring for petroglyphs. They climbed down the hole which bottomed out to a horizontal corridor. On one of the walls was carved a face out of the mouth of which poured water. Suddenly the water started to gush out of the face and from other openings, and the couple was forced to abandon the tunnel. Later, both recalled that they heard music down there.

In West Virginia, workers found some caverns with strange hieroglyphics written on the walls. They also claimed to hear faint voices and what sounded like machinery coming from beyond the walls of the cavern.

Two men searching for bat guano (which has some value as fertilizer) at the foot of Mount Lassen found a deep cave. They followed it inside for a mile or two and noticed that the floor was worn smooth, as if it had been used for a road. Eventually they met three strange "men" who asked if they are "surface people," and then took them deeper in the cave on an electromagnetically powered hovercraft. The story gets stranger from there.

Travelers Ferdinand Ossendowski and Nicholas Roerich claim to have discovered a subterranean society below central Asia, which they referred to as Agharta or Agharti. They say it is home to 20 million people, and their civilization extends throughout all the subterranean passages of the world.

A 12-man speleological team broke into an ancient tunnel system in northern Arkansas and encountered the inhabitants of the subsurface world.

Exploring another cave in Arkansas, just north of Batesville, explorers found a tunnel illuminated by a greenish phosphorescence where they met a race of beings who stood 7 to 8 feet tall and had bluish skin. The beings, who have advanced technology, told the explorers they are the direct descendants of Noah.

Brazil is said to have many entrances to an underground world. Several people claim to have proof: