Ever walk past a vacant lot or a closed down restaurant and wonder what it's like on the inside? What got left behind? Urban explorers are the kind of people that don't just wonder, they go inside. They'll explore deserted hotels, empty jails, rotting theme parks, or spelunk through sewers and mine shafts. And there have been some unsettling things waiting for them there.

Urban explorers are travelers, and urbexing is popular around the world – in Japan in particular. Japanese urbexing is called "haikyo" and economic changes in Japan have left many sites to explore. We have all imagined being that type of curious person that goes looking for treasure whenever they find a new place. We have seen some of the consequences in horror movies, but also some pretty fascinating structures that definitely were worth the explorations. Put on your haikyo hats and your urbexing goggles as we take a look at some of the creepiest places that urbex-ers have visited.

26 Six Flags – New Orleans, Louisiana

This Six Flags theme park was abandoned fairly recently, but it remains as a haunting reminder of past tragedy. Six Flags was expanding the park to include a waterpark when the infamous Hurricane Katrina hit in 2005. With a new focus on rebuilding the city, the park's building project was abandoned and the park was never reopened. It still stands vacant and is a popular haunt for urbex-ers (huffingtonpost).

25 Grossinger’s Catskills Resort – New York

Grossinger’s Catskills Resort is still waiting for visitors, but they won’t be coming. This once-popular mountain resort is overgrown, its swimming pool is filled with ice and debris instead of swimmers. It was a busy getaway for city-dwellers in the summers and one of the first to make artificial snow for skiers. Now its only visitors are urban explorers, and they don’t stay for very long (bcd-urbex.com).

24 Gulliver’s Kingdom Theme Park – Japan

In the Jonathan Swift novel, Gulliver's Travels, the eponymous hero never made it to Japan. It is now his final resting place, in effigy at least, because the Gulliver’s Kingdom Theme Park – complete with a “life size” tied down Gulliver – was built there, at the foot of Mt. Fuji, and later abandoned. The creepiest part is the park’s main attraction; Gulliver, now covered in graffiti, stares listlessly at the sky with unblinking eyes. The park was never popular and was only open for ten years. It has found a new popularity among haikyo explorers (weburbanist.com).

23 Royal Hospital – London, UK

The empty halls of the old Royal Hospital in London were once busy with the sick and ill and as much sadness as healing. That knowledge makes the dim halls of the hospital ominous for the emptiness alone. Located in Whitechapel, the building dates back to the 1750s and was once home to Joseph Carey Merrick (AKA the Elephant Man). Andy Kay, the urbexer behind Behind Closed Doors, explored the haunting operating theaters with sci-fi ceiling lights and a boarded up chapel. This hospital is also rumored to be haunted by a gray lady who wanders the halls (bcd-urbex.com).

22 North Wales Hospital – Denbigh, Wales

The deserted North Wales Hospital is the quintessential abandoned asylum on a hill, with its decaying turrets looming over the countryside. It’s the stuff of gothic nightmare, and urban explorer dreams. The mental institution known as both the Denbigh Asylum and North Wales Hospital, closed its doors in 1995, although it was slated to close in the 1960s. The main portion of the building was constructed between 1844 and 1848, and was later expanded to alleviate overcrowding. The building fell into disrepair after it closed in the mid-90s, and was targeted by arsonists. It’s crumbling halls, patient rooms, and solitary confinement cells offer a lot for urbex-ers and ghost hunters to wade through. The hospital is said to be haunted, with phantom bangs and footsteps being the most reported phenomena (atlasobscura).

21 Steinert Hall – Boston, Massachusetts

The subterranean Steinert Hall was a just legend of the Boston theater district for a long time. Was there really an underground theater downtown? It turns out the theater wasn’t a myth created by the local college students.

The street-level exterior of the building is labeled Steinert Hall, but that goes largely unnoticed above the storefronts in the building today. But 40 feet underground is the forgotten theater, originally built for piano recitals. The building was built in 1896 and was a popular concert venue before it was shut down in 1942. The peeling walls and faded murals of the water-damaged theater would make the Phantom of the Opera feel at home.

20 Big Horn Mine – California

On the side of Mount Baden-Powell lies a rickety hut on stilts that caps off the opening to the abandoned Big Horn Mine. Found by Charles Tom Vincent when he was hunting for bighorn sheep, the mineral mine was started in 1895 and was active for nearly a hundred years. The deep, waterlogged, and graffitied tunnels that wend their way into the mountain are creepy, to say the least.

19 Lenin's Young Pioneer Club – Russia

Why are larger-than-life fish and Cthulean tentacles trying to eat this otherwise unassuming brick building? You’ll have to ask Soviet Russia. Explored by Darmon Richter of The Bohemian Blog, this is an abandoned Young Pioneer Camp, one of thousands of holiday sites built and controlled by the government under the regime of the USSR. The Young Pioneers were a scout-like organization that taught children survival and life skills and how to be a good communist.

Richter and some friends found this particular camp deep in the woods north of Moscow. It’s hard to imagine anyone having fun at this nightmare camp.

18

17 Lake Shawnee Amusement Park – West Virginia

The empty Lake Shawnee Amusement park is the real-life equivalent of the ghost playground in the Goosebumps opening credits. And it’s history will give you goosebumps. Originally a Native American burial ground, the land was bought by the Clay family, who were later taken by a local tribe. The spot was turned into a small amusement park in the 1920s, but the park was hardly more lucky than the Clays. After 6 people lost their lives at the park, it was shut down. It is reportedly haunted.

16 Spreepark – Berlin, Germany

The powers to be of the time seem to have had a thing for scaring children. The now-decaying Spreepark was built in East Germany in 1969 and ceased operation when the USSR did. The park is now a graffitied landscape of large creatures with gaping mouths, ready to eat passersby, and some slightly less frightening toppled dinosaurs. It gives us the heebie-jeebies just looking at it, but it may have been a pretty fun place to be, way back when, maybe to escape some of the less-fun things of the time.

15 Ospedale di Psichiatrico di Volterra – Volterra, Italy

This remnants of this asylum could be the perfect backdrop to any Italian gothic horror film. Cryptic, peeling letters and murals are scrawled across the walls. Abandoned wheelchairs litter the property. Vandals have gone wild painting graffiti and breaking windows. Left behind in 1978, Ospedale di Psichiatrico di Volterra was built in 1888 and by the early 1900s had expanded to include shops, agricultural areas, and even an institution-specific judiciary. But the staff at the hospital also inflicted harsh and even harmful treatments on their patients, which led to the eventual closure of the asylum.

14 Gonjiam State Hospital – South Korea

Gonjiam State Hospital is truly nightmare fuel. It is the subject of a number of fantastical ghost stories. It was closed in the mid-1990s due to sewage problems, but the hunt for ghosts and the horrors that create ghosts linger. The hospital is widely considered to be one of the most haunted in the country. It is a popular stomping ground for urbex-ers and ghost hunters alike.

13 Burwash Correctional Center – Burwash, Ontario

Burwash Correctional Center is broken and unassuming, eery in its quietude, but it was once the force that built an entire town. When the prison was opened in 1914, it stood entirely alone in the Ontario countryside. But as the prison population grew, and with the construction of a nearby highway, and the staples of a town followed. When the correctional center was closed because of cost, it became a ghost town.

12 Essex County Jail – New Jersey

The mold and disrepair of this former house of corrections looks more like a crime scene itself. The ceilings are peeling like string cheese; the walls are crumbling, piece by piece; every bar is weakened with rust, and there are stains that can’t quite be identified. This long-vacant prison is a frequent fixture on lists of the United States’ creepiest prisons.

11 Grande Ballroom – Detroit, Michigan

Detroit is an urban explorer’s dream; although it’s on the upswing, huge swathes of the city were abandoned after car manufacturing moved overseas. The Grande Ballroom is one of at least a dozen theaters standing unused in Motor City, but it is one of the most beautifully decayed and spooky. The Grande Ballroom began life as a jazz hall in the 1920s, but became most famous as a sixties and seventies rock venue that hosted hometown legends like MC5 and The Stooges and other legendary acts.

10 70 Highland St Apartments – Detroit, Michigan

Businesses weren’t the only things that got left behind in Detroit. When rent became untenable, tenants had to move or were forced out. Although many are being razed by developers, apartment blocks upon blocks are left open and in states of eerie disrepair. This apartment block, one of many on Highland St, has a unique Moorish style exterior, and all the secrets of the people who used to live there.

9 Tuchthuis Vilvoorde (Vilvoorde Prison) – Vilvoorde, Belgium

Old prisons are just plain creepy. This 18th century Belgian prison, Tuchthuis Vilvoorde (or Vilvoorde Prison), proves it. Built in 1779, this prison housed nearly 200 years of military and civilian prisoners and hospital patients, many of whom scratched haunting messages on the walls, as well as pictures of crosses and a solar calendar (urbex.nl).

8 Harlingen Storage Plant – Harlingen, Texas

At the very limits of Texas, near the Rio Grande, lies this abandoned cold storage plant, a gray monolith against the landscape. The cavernous plant itself is a forest of graffiti, suggesting the crimes that have happened there since it ceased to function.

The place has become more of a social haven for teens, who use it as their own personal lair, to get rowdy and have their own space. Unfortunately, it also attracted a few hazardous fires, probably due to its unwelcomed residents (mysanantonio.com).

7 Monastery Crypt – Bulgaria

On a trip through the Bulgarian mountains, urbexer Darmon Richter (the journalist behind The Bohemian Blog) stumbled upon a monastery chapel. While the chapel appeared to still be in use, beyond a nearby graveyard was an ossuary, or bone crypt. Inside, he found the carefully labelled skulls of monks. Macabre, to be sure, but Richter said he found this crypt "moving" and "strangely comforting." Mind you, he did find the skulls in the daytime.