The workers and builders of the Harbin Ice and Snow Festival still have a lot to do. They need to shape and stack 250,000 cubic meters of ice into huge and artistic, brightly illuminated structures such as pagodas, towers and slides. The building material consists of meter-thick blocks cut from the ice cover of the Songhua River. The festival in northeastern China, north of the Russian city of Vladivostok, is celebrating its 25th anniversary and will last until the end of February, when the sun will slowly melt the intricate structures.