A room decorated with military maps and old propaganda posters in a cave that was once the headquarters of former Chinese Communist military leader Lin Biao, located in mountains on the outskirts of Beijing July 16.

A gas mask hangs next to a poster of former Chinese Chairman Mao Zedong in a cave that was once the headquarters of former Chinese Communist military leader Lin Biao, July 16.

Grenades and a tank mine sit atop ordnance boxes in a cave that was once the headquarters of former Chinese Communist military leader Lin Biao, July 16.

Old parachutes hang above tables in a cave that was once the headquarters of former Chinese Communist military leader Lin Biao,

The entrance to a cave, shaped in the form of an aeroplane, can be seen under a mountain that was once the headquarters of former Chinese Communist military leader Lin Biao located on the outskirts of Beijing July 16.

A security guard stands near a painted wall showing blue sky and white clouds on a hazy day in Beijing Monday, June 18.

Chinese activist Chen Guangcheng is seen in a wheelchair pushed by a nurse at the Chaoyang hospital in Beijing on May 2, 2012.

A man holds a sign that reads 'Free Chen Guangcheng, Democracy, China', outside an entrance to Chaoyang Hospital on May 2, 2012.

Human rights activist Jiang Tianyong speaks to journalists outside Chaoyang Hospital after his failed attempt to see Chen Guangcheng on May 2, 2012.

A model poses next to a Lexus ES 300h at the 2012 Beijing International Automotive Exhibition in Beijing on April 24.

A model poses next to a Mini Cooper at the 2012 Beijing International Automotive Exhibition in China on April 24.

The latest BMW concept vehicle i8 Spyder is on display during the 2012 Beijing International Automotive Exhibition in Chinca on April 24.

A Fiat 500C is on display at the 2012 Beijing International Automotive Exhibition in Beijing on April 24.

A Cadillac CIEL is on display at the 2012 Beijing International Automotive Exhibition on April 24 in Beijing, China.

A diabetes patient has her blood pressure taken as another patient is checked by diabetes specialist Doctor Tong Xiao Lin at the Guanganmen Chinese medicine Hospital in Beijing on March 19.

A diabetes patient sits in a wheelchair, under a drawing of an old Chinese medical scholar, as she waits in a corridor of the Guanganmen Chinese medicine Hospital to see a diabetes specialist.

The new China Central Television (CCTV) tower hardly visible as fog covers most of Beijing on Saturday. More than 400 flights to and from Beijing airport, including around 35 international services, were cancelled or delayed due to thick fog and strong air pollution covering the city, which the US embassy own measuring system, said pollution in Beijing had reached the "hazardous" level early March 17, before dropping one notch to "very unhealthy" later.

Vehicles make their way along a highway as fog covers most of Beijing on Saturday.

Passengers wait for their flights as almost 250 flights were cancelled, including some 15 international services, while more than 180 flights were delayed, including about 20 international services at the Beijing Capital International airport as visibility was at less than 200 metres (650 feet), official state news agency Xinhua said, blaming "widespread fog" for the disruption, in Beijing on Saturday.

Ms. Zhuang, a Hotel Test Sleeper, checks the bed of a business chain hotel in Beijing on Monday, March 6. Zhuang was selected as one of three final winners out of 7,800 candidates and started working for Qunar as a Professional Hotel Test Sleeper in March 2010. At present, she has slept at more than 200 hotels. "My job is to role-play travelers of different types, different ages and genders at different scenarios, and see how each hotel fits their particular needs." Zhuang said. Her reviews help travelers make smart hotel picks and bring them a more pleasant experience on the road. Qunar, a Chinese online travel platform, started to recruit Professional Hotel Test Sleepers in 2010. The requirement for this new profession is to sleep at selected hotels without disclosing their real job and write expert reviews about the facilities, location, dining, services and prices of the hotels, in order to provide an independent third-party evaluation and an authoritative guide to travelers, according to the company.

Ms. Zhuang checks a glass as part of her job as a Hotel Test Sleeper at a boutique hotel in central Beijing.

Ms. Zhuang takes a picture of slippers in the bathroom of a boutique hotel.

Ms. Zhuang, a Hotel Test Sleeper, checks the network speed of wifi on her iPad at the public area of a Beijing traditional hotel with courtyard houses, known as "Siheyuan" in Chinese.

Ms. Zhuang sleeps on the bed as she shows a part of her job as a Hotel Test Sleeper.

A woman and her son sit inside the capsule of an electric tricycle as they drive along a main road in central Beijing March 15, 2012.

Traffic police officers with neck support pillows given to them as a reward from their commander during the National People's Congress in Beijing on March 8, 2012.