In a dusty, abandoned Belgian chateau, author Ransom Riggs is putting together a puzzle. 

In his mind, he's trying to put together the left-behind pieces of people's lives. Abandoned decades ago, the chateau is dark and dusty, but not empty. In it, clues to the past lay scattered: old clothes, handwritten notes, various tools. Every item is a puzzle piece that shows a picture of the past. Who lived here? What were they like? Where did they go?
Technically, Riggs is trespassing. According to the BBC, breaking the law is just part of the excitement that comes along with "urban exploration," a type of underground hobby where people explore abandoned structures. The hobby comes with risks. Other than being arrested for breaking and entering or trespassing, explorers risk exposure to asbestos, hazardous dried bird feces and rusty nails. They sometimes wear protective respirators to alleviate health risks.

Why do it? What's the appeal in putting life and limb at risk to explore abandoned homes and factories? Most explorers liken the experience to having a childlike curiosity they never grew out of. Others have a strong love for history and architecture. 

Ransom Riggs is exploring the Belgian chateau for a different reason. In a video Riggs uploaded to YouTube in June 2011, he explains that he wanted to make sure the setting for his novel -- "Miss Peregrine's Home for Peculiar Children" -- was true to life. His journey for authenticity led him to Europe to find the kinds of houses that are described in the pages of his book.  

"There's a certain indefinable look that these old houses in Europe have," Riggs wrote on Mental Floss, "that's difficult to find in America."

When he stepped into these abandoned homes, he discovered something he never expected to see. Some of the homes, empty for decades, were completely undisturbed. If not for the thick dust coating everything, it was as if the homes were still lived in. Trinkets from a time long past littered the insides.

Riggs teamed up with urban explorer and photographer Martino Zegwaard to photograph and document the insides of these homes. In his video, Riggs explores the insides of several abandoned European houses and confides that his intention is to show that these long-abandoned homes aren't just rotting wastes of space. 

"These houses aren't graves," Riggs says. "They're secret histories, waiting to be read."

"Miss Peregrine's Home for Peculiar Children" reached No. 1 on The New York Times' Best Sellers List, and Hollywood Life reports that the book's theatrical adaptation -- directed by Tim Burton -- is scheduled to be released in March.