A jade-coloured river didn't freeze over and kept flowing even when the temperature was lower than -20C in northern China's Arxan City on November 23.

The video shows fog rising up from a flowing section of the river Khalkh, as the two banks of it have frozen solid and the colour of the river turned jade green.

According to reports, the 20-kilometre-long river never freezes in winter as it is kept warm via natural geothermic heating.

The video was provided by local media with permission.

11月以来，内蒙古阿尔山市气温持续下降，最低达零下20摄氏度以下，河面冰封，大雪覆境。近日阿尔山世界地质公园三潭峡旅游景区不冻河段惊现“翡翠”河段，冰花、雪花、水花三花竞放，碧绿的河流宛如翡翠玉魂。
阿尔山不冻河位于兴安盟阿尔山市境内，是距市区74公里处的哈拉哈河的一段河流，这处河段严冬从不封冻。
三九严寒，滴水成冰，市境内所有大河小溪皆封冻，唯有此段河水热气腾腾，流水淙淙，多少年来从未结冰，令人称奇。水中还长着青青的水草；河面上云蒸霞蔚，河岸边雾凇晶莹，景色十分壮观。
不冻河河段全长20公里，不冻河现象的产生，是由于该河段附近有大量的地热存在的原故。冬季游人来到这里，可以欣赏到这一奇特的地质景观。（视频由内蒙古台提供）