Giant bubbles could be 'built over Beijing parks to save residents from smog danger'

Beijing has the worst smog levels among the world's capital cities - so bad that playing sports outdoor is often banned - but it could get a stunning new set of lungs in the form of a covered botanical garden, retail and office complex under a giant transparent roof.

Called Bubbles, the architectural concept might seem an unlikely candidate for a high-rise city of 21 million people. But its designers believe it offers something that every urban environment needs.

"It's just an infrastructure project like building metro stations and parks - it's applicable in every dense, polluted metropolis where there's a need for open, green spaces throughout the year," says Rajat Sodhi at Orproject, an architecture practice with offices in London, Beijing and New Delhi.

Sodhi and his colleagues know all about air pollution. He comes from New Delhi, another capital struggling with grim air quality, while another designer is a native of the Chinese capital.

Last year Beijing suffered 60 days of pollution above the emergency levels as defined by the World Health Organisation, and barely any days with good air. "Everyone's always wearing masks [outdoors]," says Sodhi. "We're not meant to live like this."

Watch: A view of Beijing's smog from atop the Forbidden City