Instead of the same old beach vacation this summer, why not beat the heat by heading underground? From amusement parks in salt mines to subterranean gardens, there are a variety of fascinating underground travel destinations where you can relax, see the sights, and cool off.

1. SALINA TURDA // TURDA, ROMANIA

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Salina Turda (Turda Salt Mine) was a salt mine in Transylvania that operated for hundreds of years, up until 1932, when it was repurposed to serve as cheese storage and as a bomb shelter. In 1992, parts of the mine were converted into something more fun: an amusement park.

At 400 feet below ground, the park features an amphitheater, mini-golf, basketball courts, a bowling alley, a Ferris wheel, a carousel, and a spa. The latter takes advantage of the chambers' supposedly health-giving temperatures—a constant 54 degrees with 80% humidity—and relative freedom from allergens and bacteria. Tourists can also rent rowboats and paddle around on an underground lake.

2. RUBY FALLS // CHATTANOOGA, TENNESSEE

 

Leo Lambert bought land above the Lookout Mountain Caverns in Tennessee in 1928, hoping to open a new entrance to the caves and make some money from tourists. Instead, he found an entirely new cave that contained its own underground waterfall. Lambert named the cave and its waterfall after his wife, Ruby. Ruby Falls, located in Ruby Falls Cave, is now one of Tennessee's best-known tourist attractions.

3. UNDERGROUND CITY OF NAOURS // NAOURS, FRANCE


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Cité souterraine de Naours, or the Underground City of Naours, was originally a limestone quarry. Many centuries ago, local residents in this part of northern France discovered that the underground chambers were a great place to store supplies, hide from raiders, and find shelter from the elements. By the 17th century, the chambers had been turned into a city of 3000 people, complete with homes, chapels, businesses, meeting rooms, and even livestock facilities. Cité souterraine de Naours was abandoned as the area grew more peaceful, but was rediscovered in 1887.

4. CAVE HOMES // GUADIX, SPAIN

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Residents of the Andalucían town of Guadix began carving their homes out of limestone hundreds of years ago. They're usually recognizable by the chimneys that arise from the ground, with no houses visible underneath (some homes also have visible exteriors, but extend much further underground). Many of these homes were first built for protection from invaders, yet they are so comfortable and economical that they are still used today. While the private homes of Guadix aren't open to the public, the proud owners might grant you a peek. If all else fails, you can visit the Cave Dwellings Interpretation Centre in Guadix and learn about the history of the homes.

5. UMOONA OPAL MINE & MUSEUM AND THE SERBIAN ORTHODOX CHURCH // COOBER PEDY, AUSTRALIA

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The town of Coober Pedy, South Australia grew up around the opal mining industry. But the desert conditions are so extreme that Mad Max Beyond Thunderdome was filmed there. Daytime temperatures regularly reach into the triple digits, and can reach 113°F in the shade during summer. To deal with the extreme heat, the residents tend to build their homes underground. Abandoned chambers that have been mined of their opals are also used for underground community buildings.

The Umoona Opal Mine & Museum is the town's largest underground attraction, and a good place to learn about the history of Coober Pedy and its opal mines. The town's Serbian Orthodox Church is also quite notable, with its sanctuary carved by volunteers under a sandstone hill, along with a fellowship hall, school, and parish house—all underground. The church is open to visitors.

6. PUERTO-PRINCESA SUBTERRANEAN RIVER NATIONAL PARK // PALAWAN, PHILIPPINES

 

The Puerto-Princesa Subterranean River National Park, a UNESCO World Heritage Site, surrounds one of the longest underground rivers in the world. The 5-mile underground section of the river empties into the ocean, after flowing through a limestone cave full of spectacular formations and populated by bats, monkeys, sea snakes, and other wildlife. Tour company PPUR offers excursions to the park starting from Puerto Princesa City, about 45 minutes away.

7. FORESTIERE UNDERGROUND GARDENS // FRESNO, CALIFORNIA

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Sicilian Baldassare Forestiere immigrated to California around the turn of the 20th century, but soon found the heat of Fresno oppressive. Inspired by the catacombs near his home in Sicily, he began digging himself underground caverns in which to stay cool, and kept digging for the next 40 years. Along the way, Forestiere developed methods to deliver enough sunshine so that he could grow fruit trees and grapevines in his underground home. The result of his digging is now Forestiere Underground Gardens, where some of his original trees are still thriving 100 years later.

8. EDINBURGH VAULTS // EDINBURGH, SCOTLAND

 

After Edinburgh's South Bridge was completed in 1788, the space under its 19 massive stone arches was used for storage and small businesses such as taverns and cobblers. But as conditions beneath the bridge deteriorated (for one thing, it had never been properly waterproofed), businesses moved out and squatters, criminals, and fugitives moved in. The maze of rooms and corridors now known as the Edinburgh Vaults were rediscovered during an excavation in 1985, when evidence of past residents sparked interest in South Bridge history. The vaults are now a tourist draw, and it doesn't hurt a bit that the mysterious underground corridors are said to be haunted by the ghosts of those who used them.

9. BASILICA CISTERN // ISTANBUL, TURKEY

 

In the 6th century, Byzantine Emperor Justinianus I constructed a huge underground reservoir near the southwest corner of the Hagia Sophia in Istanbul. It was built beneath the Stoa Basilica, why is why it's known as the Basilica Cistern, or Yerebatan Sarnici in Turkish. The brick-lined chamber is supported by 336 stone columns, and can hold up to an estimated 100,000 tons of water. The cistern has been abandoned and then restored several times over the centuries, most recently in 1985. The most striking features of the cistern's architecture are the two giant Medusa heads that support two of the columns. One is placed sideways, while the other is upside down. They may have been taken from a Roman building, and placed in their unusual manner to show disrespect for pagan figures. The Basilica Cistern is now a museum, open to the public.

10. NARUSAWA HYOKETSU ICE CAVE // NARUSAWA, JAPAN

 

The volcanic activity that led to the birth of Japan's Mt. Fuji also produced caves in the ground underneath the mountain. One of these is Narusawa Hyoketsu Ice Cave in Yamanashi Prefecture. The cave is near the east entrance of the Aokigahara Jukai forest, which is also known as the "suicide forest." Narusawa Hyoketsu is so cold that water dripping from the ceiling forms pillars of icicles year-round. The average temperature inside the cave is barely above freezing, which made the cave a perfect place to store ice before mechanical refrigeration. Today, it's open for visitors.

11. MEGA CAVERN // LOUISVILLE, KENTUCKY

 

A former underground limestone quarry in Louisville, Mega Cavern spans about 4 million square feet. Much of that space is dedicated to a commercial storage business, but you might be more interested in the underground amusement park. The park includes the a 320,000-square foot bike park, a zip line, an aerial rope challenge course, and tours.

12. WIELICZKA SALT MINE // WIELICZKA, POLAND

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The Wieliczka Salt Mine near Krakow produced salt from the 13th century up until 2007, but even before mining ceased it became a national historic monument and a tourist attraction. The natural resource has figured prominently in Poland's history over the centuries, and miners created an underground world that includes chapels and artworks carved into the walls, with more added by modern artists. Wieliczka Salt Mine now has hundreds of miles of underground corridors, shafts, and chambers to see. Visitors to the UNESCO World Heritage Site can choose between several tours of various lengths and themes, visit the museum, relax at the underground health spa, have an underground meal, or see concerts and other events in the mine's chambers.