"Do you know that there is a tunnel under an alley in Beijing?" Liu Yu, a college student in Beijing, asked our reporter.

Liu found the entrance to the dungeon near Qianmen two years ago. "It looks like tunnels in fantasy movies. Now only about 1 km of it is open to the public. However, it is said that it leads to the Forbidden City," said Liu.

In fact, urban adventurers like Liu are not only content with such "tunnels". "Haunted" mansions, catacombs, deserted factories, old churches, ancient temples, and unused subway stations are all their favorites. They have set up various forums to organize adventures, and exchange information.

"Beijing has been the capital of China since hundreds of years ago, and its deep cultural back ground make it a paradise for us adventurers," said Lami (not his real name) . "We appreciate different cultures and styles of different cities in our adventures."

However, adventurers from different cities have different choices of places for adventure. For example, Shanghainese like to look into old mansions, Zhejiang people like to visit old towns, while Beijingers prefer to explore the secrets of the local Hutong alleys.

Jason (not his real name), a movie fan in Beijing, likes deserted factories, for they make him feel as if he were a hero of some action movies.

"We once went to a bio-product factory in the suburb, where everything remained the same as when it was abandoned," said Jason. "It was like a huge labyrinth."

To many people, urban adventures offer a chance of forgetting the hustle and bustle of cities, and of looking at the other side of the cities they live in, behind its luxurious and modern facade.