The 500-meter Aperture Spherical Telescope. [Photo provided to China Daily]

GUIYANG - This is the quietest tourist site in China -- no phones, cameras and cars are allowed inside. Even planes have been rerouted to avoid disturbance, but still, it draws thousands of tourists.

Since it began operation in September last year, the world's largest radio telescope, located in southwestern province of Guizhou, has received 240,000 tourists, according to local authorities.

The Five-hundred-meter Aperture Spherical radio Telescope (FAST) is a single-dish telescope, with a diameter of half a kilometer. It was built in Dawodang depression, a natural karst basin in Pingtang County, an impoverished area in mountainous Guizhou.

The telescope is used to probe space for the faintest signs of life and is sensitive to any electromagnetic interference.

Nearly 10,000 residents living in the core zone, within five kilometers of the telescope, have been relocated.

"All phones and cameras must be handed in if visitors want to enter the core area," said Liu Xingwu, a local tour operator.

"Vehicle engine ignitions also produce electromagnetic waves, so all sightseeing vehicles which enter the core zone have been modified to remove magnetic interference," said Liu.

With a total investment of 1.2 billion yuan (about $188 million), the telescope has also created a boom in tourism for the county, which is home to around 330,000 people.

An astronomical and cultural park is being extended. New theaters and exhibition centers will open ahead of the National Day holiday in October, said Shi Bangze, director of the county tourism bureau.

Shi said that any increase in tourist numbers must not interfere with scientific studies underway at FAST.

"Scientist are using FAST to probe space, and they do not want any disturbances, so tourism can only be developed on the condition that the research functions are not impeded," he said.

The county has instigated a daily cap of 2,000 visitors within the core area.

"Most travellers come on weekends and holidays. We use manual film cameras rather than digital ones to take photos of the visitors. The cameras have been tested for interference," Shi said.

"Once the daily limit is reached, we divert tourists to other scenic areas further away from the telescope," he said.