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Pilot and photographer Henk Van Rensbergen travels the world in search of the most stunning and haunting abandoned ruins. This one, a monument erected in 1981 by the Bulgarian communist party to celebrate its history, is now falling to the elements.

The area where it stands can only be reached with snow scooters in winter, when the structure itself gets covered with ice: "Buzludzha literally means 'icy', and for good reason: it is incredibly cold up there; the icy wind blows right through you," writes Van Rensbergen in his book "Abandoned Places."
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This structure was originally built in 1531, when Antwerp was a prominent commercial and cultural center in Europe. (London only got its stock exchange 30 years later.) After a fire destroyed most of it, it was reconstructed in its current form in 1872. Following decades of decay, the building has been completely restored and will open to the public in 2019.
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This 2,000-seat theater first opened in 1912, then closed in 1986 and remained unused since. Taking this picture wasn't easy, Van Rensbergen writes: "It was impossible to do this discreetly, and we made a terrible racket as we climbed over the rusty, sharp wire. On the third floor, two steps broke off and clattered to the ground. I clung to the railing and asked myself what on earth was I doing in that place."
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A dentist's chair sits abandoned in one of the most recognizable skyscrapers in the Detroit skyline, the Broderick Tower. Opened in 1928, it was favored by medical practitioners until it was seized by the state in 1981 due to unpaid taxes. It sat empty for about 30 years before a $50-million renovation plan started in 2010, when this photo was taken. It reopened in 2012 as a luxury condo.
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Mozart is said to have spent a night in this lodge in 1763. The last owner couldn't afford basic maintenance, and dust is now accumulating.

"The silence inside doesn't really spoil the fun. In the living room, several animal heads mounted on the walls stare at each other while they muse over their glorious past," writes Van Rensbergen.
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This "Colonia Montana" (meaning "mountain colony" in Italian) opened in 1928 as an affordable summer resort for working-class children from the northern regions of the country. "Inside it was as still as a mouse," writes Van Rensbergen. "Just like it probably was the day before the vacation."
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Asphalt succumbs to vegetation on a road in Japan. Asked about the weirdest experience he's had in his travels, Van Rensbergen said: "I don't believe in supernatural phenomena, but in the pitch dark corridors of an abandoned underground cemetery, on my own, I did feel a strange force resisting me going further in a certain direction. I decided to obey, out of respect to the dead."
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The Six Flags amusement park near New Orleans has been closed since Hurricane Katrina struck in 2005.

"During the day, everything looked easy-going, but when we came back at night, the entire place was suddenly transformed," writes Van Rensbergen.
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Even though it has been listed in the National Register of Historic Places since 1976, the Farwell Building in Detroit has been in a state of decay since the 1980s. After being featured in the film "Transformers: The Last Knight," it was completely renovated and is now ready to reopen.
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Ivy overtakes an old building in Henk Van Rensbergen's native Belgium. A pilot since the age of 22, he first flew as a captain for Belgium's national carrier Sabena until it went bankrupt in 2001. He now flies for TUI fly Netherlands.
CNN  — 

As an airline pilot, Belgian-born Henk Van Rensbergen was used to traveling the world. But he found a great way to supersize that passion: hunting for the most wonderful, secret, haunting abandoned places.

“I bought my first camera at age 16 and soon started making photos just to prove to my friends that I had been inside this abandoned factory or that off-limits disused hospital,” he said in an email. “Soon my attention shifted to actually capturing the atmosphere inside these places.”

Frozen in time: Abandoned wrecks from around the world

For the past 25 years he has scouted countries the world over and gotten in touch with fellow urban explorers online to find the best spots to immortalize. With several books to his name, he considers himself a pioneer of the urban exploration genre. (“Although to find the founder of it, you have to go as far back as Piranesi, an Italian artist who lived from 1720 to 1778,” he said.)

But why are we so fascinated by decaying ruins, empty roads and vacated buildings?

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Van Rensbergen's latest book is titled simply "Abandoned Places."

“It’s probably a cocktail of different things, such as living your childhood fantasies of discovering a forgotten world, a bit of melancholy and a healthy sense of adventure,” he said.

Is it ever dangerous? “Yes, it could be, especially if you break your way in, if you invade privacy, steal or break things… behavior that is not tolerated by educated explorers.”

Browse the gallery at the top of the page to see some of Van Rensbergen’s best photos.