It doesn't take long for nature and the elements to overtake the cities and towns humans have built. In an interview with , Alan Weisman, the author of the bestselling nonfiction book , described what would happen if humans no longer existed. In a house without people, "suddenly no one is there in fighting off mold, keeping the insects out, keeping the mice out, keeping the woodpeckers out, keeping the water out," Weisman said.

Many buildings are abandoned because of economic reasons or conflict. Photographer Christian Richter has spent years exploring the abandoned buildings left behind by Germany's reunification in 1990. Growing up in East Germany, formally known as the German Democratic Republic (GDR), Richter saw a lot of changes in the country throughout his lifetime.

(MORE:)

Richter began exploring abandoned buildings first without a camera. He began taking photos when his friend gave him an old digital camera. He began to take his photography more seriously in October 2011 after buying a tripod.

"It is a puzzle to find a good spot for a photograph," Richter told weather.com. "You must visit many buildings to find a great one. I fall in love with the old architecture--the decaying patterns remind me that everything is impermanent."

The photographer asked weather.com not to disclose the location of the buildings he has photographed. Many photographers of abandoned buildings feel this way, as they are afraid the beauty of the buildings may be destroyed by vandals and looters.

(MORE: )

Richter travels around Europe to find abandoned places to photograph. "The creepiest place I ever visited was one of the first — an old crematorium with old kilns and funeral chambers. There was a very strong mood there."

View the slideshow above for a selection of Richter's photographs. For more information, or .

(For More Travel, )