Now, we’re all here for one simple reason: we love travel. Maybe you’re a non-stop global jetsetter, have a job that constantly sends you all over the world, or maybe you vacation somewhere different each year. Heck, maybe you simply like the idea of travel. It’s a lifestyle that so many of us can only dream of, after all, and living vicariously can be super fun.

There are as many reasons to travel and ways of travelling as there are places to travel to. We don’t all have Kanye West’s bank balance, and we don’t all want to simply luxuriate in five-star hotels or on the deck of a cruise ship. Some of us want to get down and dirty, dive right in there and enjoy the adventure, with only a backpack and some fresh underwear to our names. If that.

Travel is, after all, exactly what you make of it. it’s an incredibly personal thing, and that’s a lot of the appeal. Whether you’re a leisurely sunseeker or a non-stop thrill-seeker, you’ll find the trip that suits you.

At the same time, though, even the bravest of us have our limitations. There are certain places in the world where visitors are strictly forbidden. Some of them are super dangerous, others are super secretive, but they’re all keeping us out for a darn good reason.

What’s the deal with Brazil’s Snake Island? Why can humans only survive ten minutes inside Mexico’s mysterious Cave of the Crystals? Buckle up, friends, and join us in this rundown to find out.

20 MYSTERIOUS: Snake Island, Brazil - The Most Dangerous Island Since Jurassic Park

Now, there’s often a perfectly good reason why nature sees fit to put certain animals in remote places. They’d just eat their dang neighbours, that’s why.

The Ilha da Queimada Grande, or Snake Island, is found about 20 miles from the shore of Sao Paulo, Brazil. It covers about 43 hectares, according to Mental Floss, and local legend says that there’s a snake for every five square meters of land. Over 4,000 of which are Golden Lancehead Vipers, one of the most dangerous species on the planet, whose venom eats clear through flesh.

Needless to say, then, the Brazilian government has forbidden all access to the island, other than special clearance for select scientists. Every few years, they’re allowed to study the island, before reporting back that, yes, there is still a whole heck of a lot of angry snakes right here.

19 TOO NERVOUS TO VISIT: Poveglia, Italy - Venice’s Plague Island

Ah, Poveglia. One of the most notorious and unfortunate places on the planet. Such a beautiful setting (a small island in the Venetian Lagoon, northern Italy), such a sad and tragic history.

The story of Poveglia reads like a mash-up of every horror movie trope you could imagine. Over its time, the island has served as a fort, a place of quarantine for victims of the bubonic plague and an asylum. The hospital was closed in 1968, and the ruins really are the stuff of spooky dreams.

I don’t think I could be paid enough to visit this one. Not that anyone’s allowed access.

18 MYSTERIOUS: Tomb Of Qin Shi Huang, China- The Terracotta Army

In the days of Ancient Egypt, as we know, the departed were greatly respected. The mummification process has become synonymous with the culture, and Pharaohs were buried in lavish tombs. These were presumed to be eternal resting places, but every single one known today has been rifled through and pillaged, either by tomb robbers of the time or in the present era.

China certainly isn’t kidding around with its ancient rituals. Qin Shi Huang, the country’s first emperor, passed away in 210 BC, and much of the burial site was excavated on its discovery in 1974. The emperor’s tomb itself, though, is completely forbidden, and the government may never allow it to be excavated (as Mental Floss reports).

17 TOO NERVOUS TO VISIT: North Sentinel Island, India - They Don’t Take Kindly To Strangers

As I say, then, some of us don’t choose to lounge by the pool on vacation. Instead, it’s all about jumping in at ground level, getting to know the locals, and trying not to embarrass yourself with the high school French you haven’t spoken a word of in fifteen years.

Usually, I’ve found, people will be welcoming to outsiders and try to point them in the right direction. North Sentinel Island is a bit of a special case, though. This remote island in the Bay of Bengal is an exclusion zone, for a very good reason: the indigenous people are very isolated and will attack any and all strangers on sight.

As The Telegraph reports, two fishermen who strayed onto the island met grim fates at the tribe’s hands in 2006.

16 MYSTERIOUS: The Vatican Secret Archives, Vatican City- Forbidden Knowledge

Vatican City, famously, is the smallest ‘country’ in the world. Boasting a population of just 1000 or so and a total area of 110 acres, it’s nevertheless an independent state. Teeny it may be, but Vatican City holds some serious power, and some serious knowledge (with some serious security too).

The Vatican Secret Archives is one of the most intriguing and exclusive vaults in the world. There are some very old and super, super important documents down here, friends.

The archives are said to cover an area of over 50 miles, according to Mental Floss, and only the small staff and very, very select scholars are ever allowed access (after a long and painstaking approval process).

15 TOO NERVOUS TO VISIT: North Brother Island, New York - Oh, Brother

Isn’t it curious how a lot of these entries have been islands? It’s almost as though that’s nature’s way of telling us to stay the heckola away.

Our next stop is New York City, where the twin North and South Brother Islands await. The former is much larger than the latter (about 20 acres compared to South Brother Island’s 6 acres, according to The New York City Parks Department), and has a foreboding history: it was the site of a hospital, which once held Typhoid Mary.

Today, it’s a bird sanctuary, and visitors are strictly forbidden lest they disturb them.

14 MYSTERIOUS: Surtsey Island, Iceland - See A Volcano At VERY Close Quarters

You know how we humans tend to be. What with all the pollution, the littering, the plastic in the oceans and such, we aren’t always the friendliest to the places we visit. This is one reason why Iceland’s remote Surtsey Island remains strictly off-limits.

It emerged above sea level in 1963, after a volcanic eruption brought it to the surface. The eruption continued until June 1967, and the obscure little island has started to be populated by flora and fauna in the years since. As with other places on this rundown, the only humans permitted on the island are the occasional scientists.

13 TOO NERVOUS TO VISIT: Dulce Base, New Mexico- Underground Exploits

So, yes. As we’ve established by now, this wide world of ours hosts all kinds of unknown, mysterious places. Along with that, predictably, come the conspiracy theories and wild ideas.

Dulce, a town near the Colorado border, is an excellent example of this. The town itself is a little place with around 2,600 inhabitants, largely Native in its origin. Beneath the surface, though, there’s something super shonky going on here.

According to List25, “...the town is believed to be home to a giant underground facility where unimaginable experiments and technologies are developed. The Dulce Base is said to be a huge subterranean compound that houses human-animal hybrids, human-alien hybrids, and extremely advanced technologies.”

So, um… there we are.

12 MYSTERIOUS: Ise Jingu, Japan- Now You See It, Now You Don’t (Again And Again)

In contrast to the supposed experimentations at Dulce in New Mexico, our next location isn’t restricted because there’s anything unwarranted going on. Far from it, in fact; this is one of the most revered and spiritual places on the planet. Next stop, Ise Jingu, Japan.

As The Telegraph explains, this is the most sacred Shinto shrines in the country. Nobody but members of the imperial family or high-ranking priests can enter. To add to the exclusive shrine’s mystique, it is torn down and rebuilt every twenty years, in homage to the idea of loss and rebirth. Fascinating stuff all around.

11 TOO NERVOUS TO VISIT: Fort Knox, Kentucky - Good Luck Getting In HERE

Well, of course. If you want a secretive, high-security and night-impenetrable place, you need look no further than the iconic Fort Knox.

This Kentucky fortress is among the planet’s most heavily-guarded places. The vaults, home to the country’s gold reserves, are defended by stringent security measures, ensuring that no single staff member knows all of the combinations to all of the various levels.

Outside of that, though, Fort Knox has welcomed outsiders in certain capacities. Movies such as Goldfinger have been permitted to film in this magnificent and foreboding location. Just stay away from that gold.

10 MYSTERIOUS: Svalbard Global Seed Vault, Norway- Always be Prepared

So far, we’ve seen a country’s riches jealously guarded by secretive security measures. We’ve seen islands that are far too dang dangerous, which we’re forbidden to visit for our own safety. This is all well and good, but the Svalbard Global Seed Vault is off limits for a different reason entirely.

Located in the side of a mountain on the Norwegian island of Spitsbergen, this seed bank has a critical purpose: storing samples of various seeds in case of a global crisis. Security measures on this enigmatic little building, which contains around one million seed samples, are designed in such a way as to prevent damage from the elements as well as keep intruders away.

9 TOO NERVOUS TO VISIT: Chernobyl, Ukraine - A Tragic Legacy

Around the world, the name of Chernobyl is synonymous with nuclear disaster. That fateful day in April 1986, the Chernobyl Nuclear Power Plant suffered an accident that the area is still feeling the effects of. It will continue to for generations to come.

Much of the land around the town of Pripyat remains deserted, though plant and animal life has begun to return. With regards to the immediate area itself, though, that’s a different story entirely. Time reports that the power plant’s director has estimated it’ll be some 20,000 years before Chernobyl is inhabitable again. The medical effects on the people of Ukraine are still being understood.

8 MYSTERIOUS: The Lascaux Caves- Stop Breathing On It!

As we’ve established, then, we humans can be a destructive lot. Some of the world’s most priceless cultural treasures are closed to us today, due to our unfortunate habit of graffitiing and/or whipping a small part off to take home as a souvenir.

Sometimes, though, the damage we cause is unintentional. Take the Lascaux Caves, for instance, a stunning ‘gallery’ of Stone Age art. Eager visitors to the caves brought carbon dioxide and heat with them, endangering the fragile works. The caves were closed in 1963, and that’s the way they’ve remained since. Sometimes, sadly, the best way to ensure we can keep something is to take it away from us.

7 TOO NERVOUS TO VISIT: Varosha, Cyprus - Not A Tourist Hotspot Any More

Ah, how the times have changed. There was a time, half a century ago, when Varosha was a magnificent and exclusive tourist resort. This beautiful spot in Cyprus was a huge hit with A-listers. According to The Express, Brigitte Bardot and Elizabeth Taylor were among the regulars at this little slice of luxury in Cyprus.

Following the Turkish invasion in 1974, however, the north of the island was occupied and Varosha sealed away. Elite vacation-takers fled from the area during the invasion and haven’t been back since. Public access is now forbidden, and the once-thriving town is now completely abandoned.

6 MYSTERIOUS: Coca-Cola Vault, Georgia - Taking Your Secret Recipe A Little Too Seriously

Now, of course, when you’re dealing with super-valuable treasures, be they monetary (Fort Knox) or cultural (Vatican Secret Archives), you are not going to mess around when it comes to security. No sir. You thought your school’s hall monitors took their duties seriously? You haven’t seen anything yet.

Now, I’m not sure that the Coca-Cola recipe qualifies as a cultural treasure, but man are they keeping it safe. At the World of Coca-Cola Museum in Atlanta, Georgia, it’s kept in the enigmatic and secretive Coca-Cola Vault. What’s guarding it? guard dogs? Laser beams? Sharks with frikkin’ laser beams attached to their heads?

Probably, yes. Mere mortals like ourselves will never know, that’s for darn certain.

5 TOO NERVOUS TO VISIT: Pluto’s Gate, Turkey - A Gate To The Underworld

What’s in a name? More than you’d think, in some cases. I mean, sure, you can’t judge solely on the bases of a name, but still. When it comes to places, I’d rather got to Barney The Dinosaur’s Super-Cutesy Adorable Funland than somewhere nicknamed the ‘gate to hell.’ Wouldn’t you?

Pluto’s Gate was discovered in 2013, on an archaeological dig in Turkey. It was once a temple, according to Fact Republic, built in honour of the god of the underworld himself. Built over a cavern in the Earth, it continues to emit dangerous gases, and tourists are forbidden to approach it.

4 MYSTERIOUS: Chichen Itza, Mexico - No Climbing Allowed

Now, of course, people are permitted to visit Chichen Itza. This archaeological site in Yucatán State was built by the Mayans, during the pre-Colombian era. It attracts tourists in their millions, but there’s one thing that they’re strictly forbidden from doing any more.

That’s right: climb El Castillo (The Castle). The focal point of the ruins, this 98ft step-pyramid has been the unwitting star of many a selfie. In 2006, a visitor lost her life after a fall from it, and so it became strictly a look but don’t touch sort of attraction. It continues to hold a certain allure about it, though, much as the Ancient Egyptian pyramids do.

3 TOO NERVOUS TO VISIT: Cave Of The Crystals, Mexico- Too Hot To Handle

While we’re on the subject of Mexico’s fascinating-yet-fatal wonders, we’ve just got to cross over to Naica, Chihuahua. The Cave of the Crystals is connected to the Naica Mine, and while it’s a little obscure, it’s every bit as fascinating as anything else in this rundown.

Discovered in the year 2000, this cave boasted a stunning display of huge selenite crystals. It was also extremely hot, reaching temperatures of 136 Fahrenheit and 99% humidity at times. As a result,  Fact Republic reports that nobody could withstand exposure beyond ten minutes or so. Even with specialistic equipment, they didn't fare much better.

Owing to the inherent dangers, the cave has since been left to re-flood, and is no longer accessible.

2 MYSTERIOUS: Uluru, Australia- It’s A Rock, Jim, But Not As We Know Them

Uluru, better known worldwide as Ayers Rock, is a quintessentially Australian landmark in my eyes. It’s a little exotic and otherworldly, it’s darn huge and it’s very, very hot there. That’s what being Australian is all about.

As with Chichen Itza, it’s a landmark that needs no introduction. One of the country’s most famous and enigmatic, it attracts tourists in droves. It was also, as with Chichen Itza’s famous El Castillo, a hotspot for climbers, until the locals decided it would be best to halt that practise. In November 2017, the decision was made to close the climb to visitors, effective as of 2019.

1 TOO NERVOUS TO VISIT: Bohemian Grove, California - Taking The Gentleman’s Club Thing Too Far

Ah, yes. Now this is the height of exclusivity, right here. You have thought that fancy resorts frequented by Hollywood stars were as extra as it got, but this is something else entirely. California’s Bohemian Grove has them all squarely beaten.

This is a vast 2,700 acre camping spot in Monte Rio, where, The Express reports, themost powerful men in the world gather… for a fortnight of drinking and secret talks and rituals.” The exclusively male membership of this club includes former Presidents and oil barons. Needless to say, a fly on the wall here would hear all manner of interesting conversations.

Equally needless to say, we mere mortals wouldn’t get anywhere near the place.

Resources: Mental Floss, The Telegraph, List25, Reader’s Digest, Traveller, Express, Fact Republic.