THIS building is so huge it could fit 20 Sydney Opera Houses inside and is three times the size of the Pentagon in Washington. It features a re-creation of a 'Mediterranean village', shopping centres, a water park, hotels, a 14-screen movie theatre and an ice-skating rink.

It even has an "artificial sun" to provide light and heat 24 hours a day.

Welcome to the New Century Global Center. The largest freestanding building in the world, it has a staggering floor space of 1.76 million square metres. According to reports, it's approximately 500m long, 400m wide and 100m high.

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Built next to an artificial lake and housing a massive water park inside, "This is an ocean city built by man," Chinese guide Liu Xun told AFP.

media_camera The design for the massive building. Picture: Janghou Group

The jaw-dropping building has just opened in a new and booming area of Chengdu, Southwestern China.

media_camera The water park is seen in the New Century Global Centre building. Picture: AFP

Chengdu is home to 14 million people.

media_camera Workers clean the glass roof of the New Century Global Centre. Picture: AFP

It took three years to complete the massive project.

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media_camera It's the world's largest stand-alone structure. Picture: AFP

media_camera Visitors explore the building. Picture: AFP

Originally published as Mega-building: Inside massive 'ocean city'