Jungles are extraordinary places. Although they cover less than 7% of the earth’s surface, and are disappearing at a devastating rate of 30 million acres each year, tropical forests are home to an estimated 50% of all living things on earth, according to rainforestfoundation.org.

However, jungles still have their secrets. There are creatures we don’t yet know about, large swathes of dense landscape still unexplored, tribes not yet documented, and ancient treasures buried below the ground. People have also wandered into the jungle, never to be seen again.

There’s a whole world of mystery lurking beneath the lush, green canopy. The lure of the unknown has attracted explorers and adventurers for centuries, who have chased legends and myths of long-lost treasure. Even the advent of satellite mapping, which has made the world a smaller place, hasn’t been able to truly reveal all that the jungle has to offer.

Ancient cities and remains of religious sites are regularly being uncovered in the jungles of Guatemala, Brazil, Bolivia and Honduras, while the legends of El Dorado and the Lost City of Z still draw archeologists and treasure hunters to the tropical forests of the Americas.

From ancient wonders to bizarre hotels, mythic monsters and more, here are some of the strangest things found (or allegedly found) deep in the planet’s jungles.

25 25. The Eighth Wonder Of The World: Sigiriya

Rising out of the jungle, standing some 180m high, is the vertical peak of Sigiriya. This dramatic rock contains the ruins of an ancient, fifth-century civilisation, thought to be once the thriving centre of the short-lived Kassapa kingdom.

The granite rock, which lies at the heart of the city’s ruins, is home to beautiful frescoes, stairs carved into the stone, and the remains of a royal palace. No wonder this astounding site is one of Sri Lanka’s biggest tourist attractions.

24 24. The Strange Stone Spheres Of Costa Rica

Dotted around Costa Rica's Diquis Delta region are giant stone balls, which scientists believe were first created around 600 AD. Around 300 of these spheres are known to exist, with the largest measuring eight feet in diameter and weighing a massive 16 tons and, according to Science Daily, no one really knows why they’re there.

The balls were first reported in the late 19th century and only became the object of scientific investigation in the 1930s. They were also the inspiration behind the giant stone ball that nearly squashes Indiana Jones in the opening sequence of Raiders of the Lost Ark.

23 23. The Lost Stone Head of Guatemala

It is believed that an unusual giant stone head once stood deep in the jungles of Guatemala. What made this head so remarkable was that it was thought to be ancient, yet its features looked Caucasian, which would be oddly inconsistent with any of the pre-Hispanic peoples who inhabited the area around the time it was thought to be carved.

According to Ancient Origins, this mysterious find came to light in a photograph sent to Dr. Oscar Rafael Padilla Lara in 1987. The seemingly authentic picture dated from the 1950s, but by the time Dr. Padilla visited the monolith, it had allegedly been destroyed by anti-government rebels. Fact or fake - the jury is still out. Either way, it raises a lot of fun questions.

22 22. The White City Of The Monkey God

For hundreds of years, indigenous peoples of Honduras have spoken of a “white house,” a paradise where local tribespeople took refuge from conquistadores. In 2015, an expedition team might just have found this “White City,” also referred to in legend as the “City of the Monkey God.”

An aerial survey of the remote La Mosquitia valley first revealed the ruins in May 2012, according to National Geographic. Archeologists have since discovered plazas, earthworks and even a pyramid belonging to a virtually unknown culture, which existed some one thousand years ago.

21 21. A Flight Of Fancy: Hotel Costa Verde, Costa Rica

It might look like a scene from the TV show Lost, but this vintage jet plane hasn’t just crashed in the jungle, it’s actually been carefully positioned there.

The Hotel Costa Verde offers a room with a view by way of a salvaged 1965 Boeing 727. Located in the dense rainforest of the Manuel Antonio National Park, this two-bedroom suite has been totally refurbished inside with teak panelling and enjoys a viewing deck overlooking the jungle.

20 20. A Hidden German Hideout In The Argentine Jungle

Among the vegetation of Teyú Cuaré Park, in the province of Misiones in Argentina, is a mysterious refuge believe to be the remains of a secret WW2 hideout.

Archeologists exploring the site in 2015 found five German coins minted between 1938 and 1941 and a fragment of porcelain with the inscription Made in Germany, according to The Guardian.

The Germans "had a secret project to build shelters for top leaders in the event of defeat – inaccessible sites in the middle of deserts, in the mountains, on a cliff or in the middle of the jungle like this,” the researchers’ team leader, Daniel Schavelzon, told the newspaper. These particular hideouts are not believed to have ever been used.

19 19. The Man Who Hid In The Jungle For Decades

When the Second World War ended in 1945, one Imperial Japanese Army officer remained completely oblivious. Hiroo Onoda, who passed in 2014, remained hidden in the Philippine jungle, evading search parties, convinced they were enemy scouts, until the Japanese government sent a delegation to meet him in 1974, which included his brother and former commander.

Once formally received of his duty, and now convinced the war had finished, he returned home to Japan and was greeted as a hero for his determination and duty to the Emperor.

18 18. The Lost City Of El Mirador

First discovered in 1926, Guatemala’s El Mirador dates back to 1,000AD and is one of the most remarkable archeological discoveries ever to be made in the Americas.

According to The Washington Post, this incredible lost city is seven miles wide, was once home to an estimated 80,000 people, and boasts possibly the grandest man-made structure in Central America - a pyramid with a base nearly 400ft long and a height of 236ft.

17 17. An Ancient UFO Spotted Above the Amazon Rainforest

While some of the entries on this list very much, definitely, 100 percent exist, the evidence for other entries is a little thin on the ground - and this definitely falls into the latter category. That said, aren’t all UFO sightings somewhat speculative?

Well, in 2016, a bizarre object was caught on satellite images hidden within the Amazon canopy in the Brazilian state of Rondonia, leaving some viewers to suggest its origins and explanation could be alien in nature.

A member of UFO investigators Secure Team 10 told The Mirror that the ‘shiny orbs' were spotted by a viewer searching through Google Maps. He added that Amazon rainforest is no stranger to reported UFO sightings.

16 16. The Mysterious Amazon Rings (Which Predate The Rainforest Itself)

They may have been used for defence, irrigation, or religious ceremonies, but what scientists now know is that the mysterious Amazon rings are older than the jungle itself.

According to Live Science, the ring-shaped ditches were constructed by the early people who inhabited the area. While archeologists would love to know their purpose and how they were constructed, the rings also raise very cool questions about the extent to which prehistoric people altered the Amazon rainforest before the arrival of Europeans in 1492.

15 15. The Maricoxi Sasquatches Of South America

Every region is home to some resident mythical beast or other, and the Maricoxi are essentially the Big Foot of South America. These ape-like beings are reportedly huge, as in 12-ft-tall huge. According to reports by explorer Colonel Percy Fawcett - who later mysteriously disappeared - these creatures could not speak except for grunts, though were intelligent enough to threaten his party with bows and arrows.

In the colonel’s book, Lost Trails, Lost Cities, he describes how he and his men were nearly attacked by the beasts, who ran away in terror when the men opened fire.

14 14. The Boiling River In The Heart Of The Peruvian Amazon

There is a river in the heart of the Peruvian Amazon that kills everything that falls into it - weirdest of all, scientists aren’t really sure why it’s so hot.

According to Business Insider, the river has only recently become known to science after geophysicist Adrés Ruzo, a PhD student at Southern Methodist University, set out to find the waterway which he’d learned about through folklore.

The river, located in a forested region called Mayantuyacu, surges at 200 degrees Fahrenheit and stretches four miles long. The fact it’s not attached to an active volcano or a magmatic system makes it all the more unusual.

13 13. Ariau Amazon Towers Hotel, Brazil

This futuristic-style hotel is a boutique property in the northwest of Manaus, one of the Rio Negro, a tributary of the Amazon River. It is the only hotel complex at tree top level in the Amazon Rainforest and consists of six towers, 288 rooms, all 10-20 metres from the rainforest floor. What’s even cooler is that they’re linked by six miles of wooden catwalks, allowing guests to walk among the jungle canopy, kind of.

This spectacular hotel has attracted an equally spectacular guestlist, including Bill Gates and Prince Charles.

12 12. The Lost City Of Giants In Ecuador

Ancient legends in Ecuador speak of a time when Giants walked on Earth and created huge cities. In 2012, a group of explorers, accompanied by a number of natives, discovered a lost city in the jungle with structures on a scale that would be considered way too big for the average human.

According to Ancient Code, the largest of the ruins was a 260-ft tall by a 260-ft wide pyramid, and many oversized, manufactured tools were said to have been discovered, allegedly so big that it would be impossible for humans to use them. Hence why this remarkable discovery goes by the name of Lost City of the Giants. Could it prove to be evidence that giants once inhabited Earth?

11 11. The Giant Serpent Sighted By US Soldiers In Vietnam

In the aftermath of the Vietnam War, rumours and reports abounded among serving US soldiers of strange and mythical creatures encountered in the dense tropical jungles. One veteran by the name of Craig Thompson reported that one day he and his platoon had been bathing in the Bong Son River when an enormous serpentine creature swam in their direction.

According to reports, the creature was around 30-ft in length, 2-ft wide, with a huge square head and covered with golden scales. Before the terrified men could fire upon the strange creature, it sunk beneath the water and disappeared.

10 10. Ancient Settlements In The Amazon

For many years, there was a general scientific consensus that the Amazon rainforest was once a pristine landscape, largely unaltered by human contact, but recent archeological discoveries have thrown this assumption into doubt.

According to The Washington Post, archaeologists discovered 81 ancient settlements in the Amazon in 2018, which may prove that the forest was managed by ancient civilisations, way before the arrival of European invaders.

These archaeological sites date from the years 1250 to 1500 and it’s thought the region of Boa Vista hides hundreds more undiscovered sites, and that as many as a million people might have once inhabited the area.

9 9. The Fairytale Magic Mountain, Chile

In the middle of the southern Andes in Chile sits a fantastical man-made volcano made from wood and stone. With a waterfall cascading down its side, a forested facade and hot tubs carved out of gigantic tree trunks, the Montaña Mágica Lodge resembles something from a fairytale.

According to the Daily Mail, this hotel is located in the heart of Patagonia’s pristine Huilo Huilo Biological Reserve, and prices range from a surprisingly affordable £150 to £260 per night.

8 8. Ancient Aeroplanes Of The Incas

Excavation sites of ancient Inca peoples and other pre-Columbian civilisations have unearthed some bizarre and wonderful artefacts. Among them are the so-called Ancient Aeroplanes - small, golden figures that resemble modern day aircraft. Of course, it’s more logical to assume that these mini works of art are representations of nature, like bees or birds, but on closer inspection, their features look very much like wings, stabilising tails and landing gears.

How is this possible, you might ask? Well, some theorists have put two and two together and come up with aliens: the Incas may have been in contact with extraterrestrials who perhaps possessed the technology themselves. Sounds totally likely, right?

7 7. The Sri Lanka Meteorite Fossils That Could Prove Alien Life Exists

When scientists in the United Kingdom analysed the remains of a meteorite that fell in the Sri Lankan jungle, they may have made a discovery of galactic proportions.

According to the Huffington Post, two separate studies have found that the meteorite might just contain fossils and algae that could be of extraterrestrial origin. If true, this discovery would strongly suggest that life exists elsewhere in space.

However, the research is not without its critics, who claim that the traces of life the meteorite contains are actually freshwater species commonly found on Earth. Could the object have been contaminated during its time on our planet, or is this proof of something much bigger?

6 6. The Baffling Man-Made Rainforest On Ascension Island

Rainforests are highly complex ecosystems which should take millions of years to develop. However, a man-made rainforest on Ascension Island has sprung up in just 150 years, much to the surprise of scientists.

As reported by The Independent, the forest on Green Mountain sprang up from a bag of botanical scrap brought over by the British Royal Navy in 1843. These newly introduced species have thrived in an area that Charles Darwin once described as "entirely destitute of trees,” which has led to a rethink of conventional ecological theory.