Today, our civilization is mostly concerned with what goes on above ground. Our cities are bustling cosmopolitan centers for commerce and business transactions; rarely, if ever, do we consider what might be lurking right underneath our feet, under the very streets of the places where we play and work.

But they are there: massive, intricate tunnel systems, hiding places, buildings - and all below ground. Some are only a hundred years old, others centuries, but all are fascinating.

Underground Cities in America: Portland

Imagine, it is 1908 and you are a big, brawny man satisfying your thirst with a few frosty mugs of beer in your favorite neighborhood bar in Portland, Oregon. A few more beers with all your friends, and things get rowdier as your buddies get more intoxicated. You laugh, swap jokes and stories, and soon all of you are swaying on your feet. With a belch and a wipe of the mouth with your sleeve, you set down your mug and are on your way to the bathroom, trying to weave somewhat of a straight line. Suddenly, a trap door opens underneath your feet and you plummet feet first into darkness. A mattress breaks your fall, but you are now in a cage, with broken glass strewn about outside. The trap door swings back up, locks into place, and your friends are none the wiser. Your shoes are taken so in the unlikely event of escape, the broken glass will cut your feet and leave a trail of blood for your captors to follow. You have just been 'Shanghaied.'

This scenario was all too common in Portland from the year 1850 to 1941, where able-bodied men were dropped through trap doors in bars or the dead-ends of alleys and into the Portland Underground Tunnels, or the 'Shanghai Tunnels.' These tunnels were intricately connected catacombs that extended for miles underneath the city and were used by Shanghaiers, bootleggers, white slavers, and opium den owners. The shanghaied men would find themselves on a ship bound for the Orient as sailors who endured scanty rations and terrible living situations.

The white slavers would kidnap girls as young as 14 and force them into prostitution, but not before confining them to complete darkness in a tiny little cell, barely big enough to move in - in order to break down their minds, spirits and wills before selling them off to the highest bidder.

Havre Beneath the Streets

In Havre, Montana there is an underground section that catacombs underneath the city in a series of secret passageways. Rich with history, 'Havre Beneath the Streets', as it is called, was the home of many turn-of-the-century businesses. Some of these included the Sporting Eagle Saloon, Wah Sing Laundry, Wright's Dental Office, Boone's Drug Store and a bordello.

As with Portland, these tunnels were often used for seedy purposes, including the illegal transport of liquor during prohibition. The passageways themselves were built by early Chinese immigrants, who used them to escape persecution above ground as well as to house their businesses, including a prolific opium market with opium dens.

In the Bordello, otherwise respectable citizens of the city could escape through the tunnels undetected, and employ one of the 'Ladies of the Night' for one to four dollars, depending on the desirability of the woman.

Underground Cities In Europe

Paris: The Catacombs

The Catacombs under Paris, France are world-famous - they spiderweb more than 300 feet beneath the city streets. A part of this vast labyrinth is in fact a limestone quarry that has been harvested to make the buildings, sidewalks, monuments and bridges.

A part of these catacombs have become a mass grave for more than 6 million people: the wealthy or poor, the insane and sane, the pure and corrupt--death is indeed the great leveler of humanity. Bones are indiscriminately piled atop one another without thought to who they belong to, only for how to save the maximum amount of space. During the Revolution, when land was scarce and the cemeteries overcrowded, the government decided to move the bones of the dead to the empty quarries.

Visitors can see the catacombs by entering through a simple black door, head down a staircase, past a gallery, and finally through a chamber where a sign reads in French: 'Stop - this is the Empire of Death!' And still the bones fill only a fraction of these meandering tunnels, which come with a heavy fine if you are found exploring one. Those who take it upon themselves to adventure into the catacombs despite the hazards and possible fines are called 'Cataphiles.'

Underground cities in Cappadocia, Turkey

The underground cities of Cappadocia were carved out the native rock largely due to the lack of trees for building material. As a result, the subterranean settlements are multilevel with built-in ventilation shafts, about 18 stories deep, and at one time housed over 20,000 people. Most of the cities had stables for horses hollowed out of the same volcanic rock, as well as churches, water tanks, wine cellars, tombs, missionary schools, study rooms, vertical staircases, and millstone doors that could be rolled across to seal the entrance.

The earliest description of Cappadocia can be found in the Greek mercenary Xenophon's work called Anabasis. "The houses were built underground," he wrote, "the entrances were like wells, but they broadened out lower down. There were tunnels dug in the ground for the animals, while the men went down by ladder. . ." Mostly, these urban complexes served as refuge for the Hittites, who used them in defense against raiders. This enigmatic civilization, according to historians, vanished into thin air after ruling for nearly 800 years.

It is being reported that underneath the Giza Plateau is an enormous and complex underground system complete with natural caverns, snaking passageways, ancient chambers, subterranean rivers, and hydraulic underground waterways.

This 'City of the Gods' was purportedly discovered after the declassification of SIRA, a ground-penetrating radar, which has been mapping these subterranean features since 1978. A crew led by scientist Dr. Jim Hurtak has explored the megalithic metropolis, risking life and limb to penetrate into the massive chambers (supposedly bigger than our largest cathedrals), in hopes of securing ancient artifacts and caches of Egyptian records.

This has been thought to be the same labyrinth described by the Greek historian Herodotus: "There I saw twelve palaces regularly disposed, which had communication with each other, interspersed with terraces and arranged around twelve halls. It is hard to believe they are the work of man. The walls are covered with carved figures, and each court is exquisitely built of white marble and surrounded by a colonnade. Near the corner where the labyrinth ends, there is a pyramid, two hundred and forty feet in height, with great carved figures of animals on it and an underground passage by which it can be entered."

There have been many speculations as to what the City of the Gods was used for; some argue that here the Egyptians were educated in their mystery schools, still others believe that the crisscrossing tunnels were used as an ancient subway system. What we do know is that there was an expedition that explored the underground city and made a documentary about their discoveries named "Chambers of the Deep." The film was shown to private audiences, but for reasons unknown, withheld from the general public.

Due to a reader's suggestion, Coober Pedy, Australia is being added to the list of underground cities. This remote location was used for filming in the movies Mad Max Beyond Thunderdome and Red Planet. It is one of the only places in the world to have a golf course with no grass, and the only tree is one made by welding together scraps of iron.

There are underground churches, houses, hotels, bed and breakfasts, and some of the houses even have underground swimming pools. Here the reason for living underground is to conserve energy and to get away from the heat, which can skyrocket up to over 55 degrees Celsius (131 degrees).

Coober Pedy is known as the opal capital of the world. One man who was building himself an underground home with seventeen rooms found enough opals during excavation to pay for the entire thing. Now that's smart building!