Written by Marianna Cerini, CNN

When Romain Veillon went to Italy five years ago to photograph the country's abandoned mansions, he was struck by the forgotten frescoes covering most of the crumbling villas.

Lined with dust and surrounded by detritus, they covered corridors and filled entire rooms from floor to ceiling. Once vibrant colors had faded but the scenes were still clear and exuded a grandeur that the French photographer became obsessed with preserving.

Veillon's new photographic series, titled The Imaginary Museum, captures abadoned frescoes across Europe. Credit: Romain Veillon

"They were beautiful remainders of a golden era, completely left to rot and vanish," Veillon said on the phone from Paris. "I felt this urge to document them, before they're gone forever."

That urge turned into a recently published photographic series, titled The Imaginary Museum, which captures Veillon's expeditions to empty estates across Europe. Besides Italy, the photographer has traveled to France, Portugal and Ireland, researching historical palaces and homes once known for their art and friezes.

"Research is what took most of my time," he said. "I scoured online archives and books, and talked to countless locals and friends to help me locate some of the frescoes. Occasionally, though, I also just stumbled upon them: you'd be surprised by how many dilapidated Italian farms -- probably villas that were later repurposed -- hide stunning oil paintings."

His photos shed light on the tastes and inclinations of Europe's former elite. Credit: Romain Veillon

The decaying homes reflect their former occupants' religious beliefs and personal preferences with scenes of tropical vegetation, bucolic landscapes and even exotic animals (Veillon was surprised to find the image of a monkey in one of the houses). Combined, they shed light on the tastes and inclinations of families who were once among Europe's elite.

For Veillon, they are also testament to the central role art played in the past. "These paintings show artistic canons we usually only associate with pieces in big-name institutions or famous castles and churches. They're telling of how important art was for people back then. They could easily be museum pieces too -- which is why their decay feels almost absurd."

To that end, the photo series aims to serve as an archive for posterity. "Some of the mansions I visited are slated for demolition, others have been damaged by graffiti and looters. Many are just left to waste away. With my photographs, their memory won't go completely lost."

Veillon has been fascinated with abandoned spaces since he was a child. Growing up, he used to explore forsaken structures near his house -- from his grandmother's older truck factory to abandoned swimming pools and buildings. He loved the thrill of it, but also learning about the stories and histories of each place.

When he became a professional photographer, he kept returning to the idea of derelict subjects, and eventually made it the core of his work. For the last eight years, he has immortalized everything from forgotten churches to deserted theme parks, empty hotels and decaying schools.

"Every time I enter an abandoned space, I feel both privileged to be able to witness what's left of it and sad that others won't be able to. It's a bittersweet condition."

Veillon, who has been fascinated with abandoned places since he was a child, kept returning to the idea of derelict subjects, and eventually made it the core of his work. Credit: Romain Veillon

That, he said, is all the truer for the frescoes. "They are masterpieces, and people don't even know of their existence. But what's also strange, to me, is the contrast between the liveliness they display and probably witnessed, and the eerie silence they've been plunged into."

The photographer says, while he wants other people to see and appreciate the frescoes, he'll never reveal their location. The Imaginary Museum is the closest most people will get to the real thing.

"It's a rule I follow with every project I do," he explained. "Too many times I've seen people trespassing empty sites only to steal objects, splatter them with street art, or 'be cool.' So yes, as much as I wish things were different, I'd rather keep them to myself than see them vandalized."

The photographer says, while he wants other people to see and appreciate the frescoes, he'll never reveal their location. Credit: Romain Veillon

Veillon is returning to some of the first mansions he photographed, to see if the paintings are still there.

"The fact that they are surviving -- if and when they are -- is what is really exceptional about them to me. They are a pure representation of beauty -- even if they'll eventually disappear."

When they do disappear, Veillon wants their memory to be preserved in his photos, as a historical record to show future generations the everyday beauty of the past.

"Their purpose, in a way, is to be a memento mori: a reflection on mortality, life, and the ephemerality of it all."