At some point, it might seem that we know so many things about this world that there is nothing mysterious left in it. Science can explain a lot of things, from the formation of the most bizarre natural structures to the way certain phenomena occur. We might think that absolutely everything in this world is now opened to us. Yet it is teeming with unsolved mysteries, and even though some of them can be explained from a scientific point of view, they still attract those of us, who like enigmas.

Some of these mysterious places are natural, while others are man-made. Some of them have existed for centuries, while others came to being only several decades ago. Some of them are believed to be haunted, and others are inhabited by aliens or representatives of a legendary race. We have no idea about the nature or purpose of many of these places, and a good few of them are linked to old legends and myths. And, guess what, all of these places are located in a single country and you can visit all of them if you want to rattle your nerves!

Before you start reading this list, I have a request for you. Do me a favor and forget everything you believe in, even if you are a scientist, who operates data and has a rational way of thinking. Open your mind to the mysteries of this world for a moment and you might even notice that you like it! After all, nothing sparks imagination like an unexplained phenomenon.

Are you ready? Then behold the most mysterious sites of the United States!

20 Eternal Flame Falls, Chestnut Ridge Park, New York

If you hike around waterfalls in Chestnut Ridge Park, you'll certainly notice a weird thing about one of them. There's a strange, orange-red light behind the water that looks like a flame. It can make you think that you're seeing some kind of an optical illusion, because how can something burn in the water?

But, in fact, it's not an illusion. There's an actual flame burning in this waterfall.

How does it happen? The thing is, there's a small nook behind this waterfall that emits flammable ethane and propane gas. Occasionally, the flame extinguishes, if too much water gets on it, but it can easily be lit back because the gas supply is constant.

19 Racetrack Playa, Death Valley, California

Race Track Playa in Death Valley National Park is a place, where something strange is happening to the stones. They seem to be moving by themselves, without any human or animal intervention, leaving a trail in the mid-surface behind. No one ever saw the movement of these stones, which makes it all even more mysterious.

In fact, this unusual phenomenon has a scientific explanation. Scientists say that the combination of natural forces, such as ice, water, and wind, are to blame for this. At first, rainwater collects in the dry lake bed, then it freezes as temperatures drop and create a thin layer of ice on the stones. When it breaks up, the wind pushes the stones and they move, due to being covered with ice.

18 Roswell, New Mexico

Roswell is a famed place for mystery lovers. It's suggested that the UFO crashed onto this site back in 1947 and a local ranch owner found the debris on his property. At first, an intelligence officer claimed that it was remains of the UFO and the news immediately got to the front pages of newspapers. But then U.S. military officials claimed that it was just a weather balloon.

At first, people believed the official version, but in the 1970s they started thinking that the government found aliens on the site and covered the accident. In the 1990s, another claim from the government came. This time, they admitted that the crashed object was a nuclear test surveillance balloon from a top-secret project.

Due to all these twists and turns, it's hard to believe which version is truthful and the site is still surrounded with mystery.

17 Devil’s Tower, Wyoming

Devil's Tower is an extraordinary geologic structure protruding out of the rolling prairie around the Black Hills. This site is considered to be sacred to the Native American tribes living in the area.

The main mystery about Devil's Tower is the countless parallel tracks going all along the rock. According to a legend, they were made by the claws of a giant bear that was trying to climb the mountain, because it wanted to eat the children hiding from the predator on its top.

Meanwhile, according to scientists, the origin of this formation is natural and is due to volcanic activity and erosion. But the exact way it formed remains unknown.

16 Energy Vortexes, Sedona, Arizona

Most likely, you know Sedona, Arizona, for its splendid red sandstone rock formations. But did you also know that this place is a spiritual hotspot? Some people come here not only to admire the landscape, but also to get an energy boost, due to the so-called vortexes, or areas of concentrated energy that are claimed to boost healing and encourage the feeling of well-being in visitors. Due to the strong energy produced by these vortexes, even trees twist in a very unusual way (you can see an example in the photo above).

The origin and nature of these vortexes still remain a mystery to us.

15 Old Faithful, Yellowstone National Park, Wyoming

The most mysterious thing about Old Faithful, a geyser in Yellowstone National Park, is the fact that it erupts every 90 minutes like clockwork. The eruption typically lasts for about 5 minutes and in 90 minutes everything repeats again. Scientists still don't know what causes this incredible regularity, but studying this interesting phenomenon, they are trying to understand its nature, as well as the nature of other geysers all over the world.

Thus, a secret egg-shaped chamber was found in the rocks beneath the geyser. Something resembling a pipe connects it with the mouth of Old Faithful. After every eruption of the geyser, water levels increase and steam bubbles emerge to later explode and start an eruption.

14 Skinwalker Ranch, Utah

The site of numerous paranormal activities, Skinwalker Ranch was even called "the strangest place on earth" by some visitors. Mysterious stories about this place have been told for decades. Even the Native American Ute tribe has old legends about weird "skinwalker" creatures living there.

Once a family moved to the ranch and soon started noticing a number of bizarre events, from crop circles and strange lights to poltergeist activity and UFO-spottings. They even claim to have seen a gigantic spaceship and 7-foot tall man! Needless to say, they soon left the ranch.

Now this place is a scientific research center. It's interesting that even the scientists, who work there, confirm the bizarre claims and say that they also saw UFO and noticed poltergeist activity.

13 Coral Castle, Homestead, Florida

The Coral Castle was built by Latvian immigrant Edward Leedskalnin, who claimed that to build it he used the same methods as Egyptians did to construct the Great Pyramids. It took him over 25 years to complete his work. Overall, he utilized 1,000 tons of limestone boulders to construct the house. Some of the stones weighed as much as 15 tons. It remains a mystery how he managed to move the boulders by himself and it's even been claimed that the guy must have known how to levitate them since no one even saw him operating the construction ground.

Another mystery about the construction of the Coral Castle was that no mortar was used to build it.

Leedskalnin never shared how he built this structure and, unfortunately, this secret died with him.

12 Trans-Allegheny Lunatic Asylum, Weston, West Virginia

In 1864, the Trans-Allegheny Lunatic Asylum started accepting patients. At first, everything was fine, but with time it started getting more and more patients so that in the 1950s the facility that was designed to hold 250 patients reached its peak housing over 2,400 persons. Due to this harsh overcrowding, conditions in the asylum became inhumane, including the lack of heat and caging of some of the patients. It all led to extreme violence from the patients, who began attacking the staff and making fires.

In 1994, the asylum was finally closed, but it's believed to still be inhabited by the souls of its patients. If you want to check whether these claims are true, take a ghost tour to the facility. Or are you scared?

11 Oregon Vortex, Oregon

Something really strange is happening to this place: people's height suddenly changes, they feel vertigo and can't stand straight, while brooms are standing on their own, and animals are trying to stay away from this house. Even though people have been visiting the House of Mystery in Oregon Vortex since the 1930s, scientists still can't explain the phenomena occurring there. They have something to do with a strong magnetic gravitational force, but we still don't know anything for sure.

It's noteworthy that Native Americans referred to this place as Forbidden Ground. So... do we really need to explore it, or should we better leave it a mystery?

10 San Fernando Cathedral, San Antonio, Texas

San Fernando Cathedral in San Antonio is the oldest church in the state of Texas. During the day, it can be called a stunning example of Gothic Revival architecture. But when the night falls, everything changes.

It all started in 1936, when construction workers, who were renovating the church, found bones and scattered military uniforms buried near the altar. Some believed that it all belonged to three soldiers of the Alamo. Since then, visitors started reporting that they had seen shadowy figures and even ghosts in the church. They also claimed that the figures they saw were dressed in hooded clothing that resembled a monk's robe.

9 Bighorn Medicine Wheels, Wyoming

Bighorn Medicine Wheels in Wyoming is one of the most well-preserved locations that were sacred for the Native Americans. One of the few things known about this place is that it represented harmony for the Native American tribes and was used to perform certain rituals. Everything else remains a mystery. We don't have any written record as to how and why Medicine Wheels were used.

Nevertheless, there are two theories about the Medicine Wheels. According to one of them, wheels had important cosmological and stellar alignments, while another one says that the site was used for holding special ceremonies the purpose of which has long been forgotten.

8 Mel's Hole, Manastash Ridge, Washington

In Manastash Ridge, near Ellensburg, Washington, there's a so-called Mel's Hole that boggles the minds of mystery lovers. First of all, it's still unknown whether this hole has a bottom. Due to this, some people claim that it's not a hole, but a tunnel, which reminds us of the "Hollow Earth" theory that appeared back in the 17th century. Secondly, whether it's a hole or a tunnel, it has to end somewhere or lead to someplace. We still don't know either of these things.

And third, there're claims that Mel's Hole can reanimate animals that appeared after a local man threw his dead dog's body into the hole and soon the dog came back home, alive, from the woods.

7 Winchester Mystery House, San Jose, California

Let me tell you a story. There was a woman called Sarah Winchester. Her father-in-law was a famed manufacturer of Winchester rifles. Suddenly he passed away and soon Sarah's husband and the infant passed away, too. The woman went to a clairvoyant, who told her that her relatives were killed by the ghosts of those, whose lives had been claimed by Winchester rifles. To save her own life, Sarah was told to move away and build a new house.

So she moved to San Jose, California and built a mansion that still boggles the minds of visitors. The house has doors that open onto brick walls, stairs that lead into the ceiling, as well as windows that may take you to secret passages. Supposedly, it all was constructed to ward off evil spirits.

6 Ringing Rocks Park, Bucks County, Pennsylvania

Have you ever thought that you could ring rocks, like bells? Most likely, such a crazy idea never came to your mind. But, in fact, you can ring a rock, if you go to a park in Bucks County, Pennsylvania. You're going to find a large field of boulders there and if you strike one of them, you're going to hear a ringing sound, as if it's hollow and made of metal.

Scientists say that the boulders are made from diabase, a special volcanic substance, but it still doesn't explain why they sound like bells. The boulder field location also doesn't provide any explanation to this strange phenomenon.

Whatever the reason is, this place attracts many people who like bizarre things. Coming there with small hammers in hand, they attempt to perform their own "rock" concerts and have a lot of fun.

5 Pine Barrens, New Jersey

Pine Barrens is a heavily forested area that spreads over one million acres in New Jersey. During the Colonial period, this area had a lot of swamps, paper mills, and other industries. But when coal was discovered in Pennsylvania, people moved away and abandoned this place.

Some people say that the ghost towns they left behind themselves are now inhabited by supernatural wanderers. For example, there is a so-called Jersey Devil that is considered to be the most popular resident of Pine Barrens. A legend says that he was born in 1735 as the thirteenth child to his mother. He was born with a goat's head, hooves, and leathery wings. Ever since the Jersey Devil has reportedly been creeping out the residents of South Jersey and killing livestock.

4 Mount Shasta, Redding, California

Mount Shasta is located in Cascade Mountain Range, in Redding, California. Known as one of the world's cosmic power spots, this mountain has long attracted Native Americans, Buddhists, and other spiritual seekers and mystery lovers.

Different mysteries have been spotted on and around Mount Shasta, including UFO sightings, crystal caves, and encounters with Ascended Masters. Native Americans believed that the Spirit of the Above-World dwelt on the mountain. Besides, some people claim that they saw the Lemurians - survivors of an ancient super-race that lived on Earth thousands of years ago during the time of Atlantis. There's even a legend saying that these advanced beings created a hidden city there after they lost their continent.

3 Horseshoe Canyon, Canyonlands National Park, Utah

Horseshoe Canyon isn't only a beautiful place climbing and trekking enthusiasts strive to visit. It's also a mysterious place, noted by the unique rock art that dates back 2,000 to 8,000 years. But it's not their age that creates a mystery around the pictographs. It's what depicted on them that bewilders anyone who comes to Canyonlands National Park.

The Great Gallery of Horseshoe Canyon features a large panel with human-like creatures depicted on it. These creatures have big eyes and antennas, and some of them don't have arms or legs. A lot of people suggest that they are the drawings of extraterrestrial beings, who came to visit hunters-gatherers, who lived in the area.

Is it true? Guess we'll never know!

2 Georgia Guidestones, Georgia

In 1979, Robert C. Christian proposed his project to the Elbert Granite Finishing Company. This project was named the Georgia Guidestones and it was to become one of the most mysterious sites in the USA. The company built everything as Christian wanted and now the main structure consists of four large granite slabs, standing erect around the fifth granite slab. Inscriptions are made on each one of the eight granite faces and they feature 10 Guidelines for the Age of Reason written in different languages in each one of the faces. The eight languages represented are English, Spanish, Swahili, Hebrew, Hindi, Chinese, Arabic, and Russian.

Right after the structure was completed, Christian disappeared and left us puzzled about the purpose of his creation and about his own true identity.

1 Myrtles Plantation, St. Francisville, Louisiana

Myrtles Plantation was built in 1796 by General David Bradford and these days it's considered one of the most haunted places in the USA. It is rumored that the house was built on a burial ground of Native Americans. Because of it and due to some other instances, at least 12 ghosts inhabit the place and there are numerous stories and legends about them.

Let me share one of them with you. There was a slave named Chloe, whose ear was chopped off because she was caught eavesdropping. Chloe decided to take revenge on her master and poisoned a birthday cake, thus killing two of his daughters. After it, her fellow slaves hanged Chloe. Her soul didn't find peace and now she's reportedly wandering around the plantation, wearing a turban to hide her severed ear.

So are you ready to explore some of these mysterious places by yourself?

References: Smart Travel, Huffington Post, Travel + Leisure, Conde Nast Traveler, Arizona Leisure