The 31st Harbin International Ice and Snow Sculpture Festival opened on Monday in the city of Harbin, Heilongjiang, northeastern China. The event is recognized as the largest of its kind in the world. The Festival officially lasts for one month, but with winter temperatures in the city averaging a bone-chilling minus 17 degrees Celsius, many of the sculptures remain in place for considerably longer than that. The sculptures are formed either from compacted snow, or blocks of ice which are hauled out of the nearby Songhua River. Purified water is also used, frozen into blocks of clear ice. Many of the sculptures are illuminated to add another dimension to the displays during the long hours of darkness at this time of the year. The Festival began in 1963 and became a regular event in 1985.