Every winter, a magical city made of ice glows brightly in north-eastern China's Heilongjiang province.

Ice castles, towers and fantastical structures illuminated with coloured lights form the centrepiece of the Harbin International Ice and Snow Sculpture Festival.

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People visit enormous ice sculptures illuminated by coloured lights during a trial run ahead of today's (5 January) opening of the 31st International Ice and Snow Festival in the northern Chinese city of HarbinKim Kyung Hoon/Reuters
harbin ice and snow festival
Fred Dufour/AFP
harbin ice and snow festival
Kim Kyung Hoon/Reuters
harbin ice and snow festival
Kim Kyung Hoon/Reuters
harbin ice and snow festival
Tourists sit on a horse-drawn carriage in front of ice sculptures illuminated by coloured lightsKim Kyung Hoon/Reuters
harbin ice and snow festival
Kim Kyung Hoon/Reuters
harbin ice and snow festival
Visitors walk past a train-shaped ice sculptureKim Kyung Hoon/Reuters

The blocks of ice used to create the vast structures are cut from the nearby Songhua River. De-ionised water is used for some structures, making them transparent.

The event, which also features the world's largest snow sculptures, has become hugely popular, drawing around a million visitors every year.

harbin ice and snow festival
Visitors look at huge snow sculptures during the Harbin International Ice and Snow FestivalFred Dufour/AFP
harbin ice and snow festival
People walk around a maze made of ice bricksKim Kyung Hoon/Reuters
harbin ice and snow festival
A visitor poses for a souvenir picture with an Arctic foxKim Kyung Hoon/Reuters
harbin ice and snow festival
People race each other on slides made of iceKim Kyung Hoon/Reuters
harbin ice and snow festival
Fred Dufour/AFP
harbin ice and snow festival
Fred Dufour/AFP
Harbin ice festival
Workers cut ice blocks from the frozen Songhua river, to be used to create the huge sculptures at the ice festivalAFP
harbin ice and snow festival
Workers give the finishing touches to a snow sculptureChinaFotoPress/Getty Images
harbin ice and snow festival
Workers polish a snow sculptureReuters
harbin ice and snow festival
Kim Kyung Hoon/Reuters

Harbin is one of coldest cities in China and is commonly referred to as "the ice city." The average temperature in winter is -16.8°C (1.8°F) and lows of -35°C (-31°F) are not uncommon.

The 31st International Ice and Snow Sculpture Festival runs in the city of Harbin from January 5 to February 25, 2015.