Photo: Cavers inside massive cave

The oldest part of Mammoth Cave in Kentucky was formed 10 million years ago, 9.5 million before Homo sapiens made an appearance.

Photograph by Stephen Alvarez/National Geographic Stock

From the National Geographic book Journeys of a Lifetime

  1. Underground City, Montreal, Canada

    Take one of the 120 entrances into the largest man-made underground network in the world. About 500,000 people a day use its 20 miles (32 kilometers) of shopping malls, hotels, banks, offices, museums, and universities; there are also metro and train stations, a bus terminal, and an ice-hockey arena.

    www.montreal.com
  2. Mammoth Cave National Park, Kentucky

    Place-names such as Grand Avenue and Frozen Niagara give a notion of what’s in the world’s longest cave system. The oldest part was formed 10 million years ago, 9.5 million years before Homo sapiens made an appearance.

    www.nps.gov/maca
  3. Aktun Chen Eco Park Caves, Yucatán, Mexico

    Walk by subterranean rivers (locally called cenotes) and peer through deep, crystal-clear water to the white floors of natural wells. Peace reigns in this surreal world of spectacular rock formations, stalactites, stalagmites, fossils, and fruit bats lying beneath untouched rain forest. Explore by foot or by scuba diving.

    www.aktunchen.com
  4. Cu Chi Tunnels, Vietnam

    Crawl through a small trapdoor into narrow, stifling tunnels and enter an “underground village” with kitchen, dormitory, meeting room, and hospital. During the Vietnam War (1954-75) thousands of Viet Cong were based in the 125-mile (200-kilometer) network of tunnels. The “village” was never captured despite being bombed many times.

    www.sinhcafevn.com
  5. Hannan’s North Mine, Kalgoorlie, Australia

    Descend 100 feet (30.5 meters) in a cage elevator to tunnels dug during Australia’s 19th-century gold rush. Try your hand at panning for gold. Kalgoorlie still produces 10 percent of the world’s gold.

    www.mininghall.com

  1. Wieliczka Salt Mine, Kraków, Poland

    It all started when salt was the medieval equivalent of today’s oil. Nine centuries of mining have produced miles of subterranean passages and gigantic caverns to a depth of 440 feet (134 meters). More than one million people a year visit the UNESCO-listed site, which features lakes, chapels and statues sculpted from salt, the world’s largest mining museum, a sanatorium for those suffering from asthma and allergies, and concert halls with peerless acoustics.

    www.krakow-info.com/wielicz.htm
  2. Berlin Nuclear Bunker, Germany

    Take a few minutes to adjust to the dim light of this 1971 radiation-proof Cold War bunker. Feel the cold creep into your bones in the deathly silence. Tiers of narrow bunk beds for 3,562 people take up most of the space. The bunker could operate for 14 days, after which you would be cast out into the radiation-saturated debris of Berlin after a nuclear attack. It’s a spine-chilling experience.

    www.story-of-berlin.de
  3. The Paris Sewers, France

    Every day 42 million cubic feet (1.2 million cubic meters) of wastewater gush through this 1,300-mile (2,092-kilometer) system. See 457 feet (139 meters) of sewer at work (with attractions including a manual flusher trolley that keeps detritus on the move) and learn about waste disposal through the ages. The smell is only a tad tangy and postcards are available, according to one guide, from a “sewer-venir store.”

    www.paris.org/Musees/Egouts
  4. The Catacombs, Rome, Italy

    Walk the galleries, chambers, and churches of the necropolises beneath the Eternal City and imagine it in the early centuries of Christianity, when Rome was a dangerous place for believers and the caverns were lit by a myriad of flickering oil lamps. Don’t miss the graffiti—thousands of prayers written by anyone from popes to plumbers.

    www.showcaves.com
  5. The Great Pyramid, Giza, Egypt

    Descend 330 feet (101 meters) through a 3.5-foot-wide (1-meter-wide) passage into the heart of the only wonder of the ancient world that survives to this day. Inside the awesome inner sanctum is a sarcophagus, built of granite from Aswan, 625 miles (1,006 kilometers) away. About 5,000 years old and 30 times larger in area than the Empire State Building, the Great Pyramid has been the subject of centuries of speculation about its origins, construction, and purpose.

    www.egypt.travel

Share

Related

  • Photo: Snowy trees in a mountain pass

    Ski Runs & Lodges

    Grab your gear: These are the best places to hit the slopes and relax in front of a blazing fire.

Back to Top 10 Main »

Take a Nat Geo Trip

Select a destination or trip type to find a trip:

See All Trips »

Join Nat Geo Travel's Communities




2014 Traveler Photo Contest

  • Picture of people on the Salar de Uyuni, Bolivia

    Enter Today to Win!

    Submit your best shots for a chance to be featured in our weekly galleries and to win a grand prize trip for two to Alaska.