Chinese environmental scientists recently identified the thinnest river in the world, only a dozen centimeters at its widest, on the Inner Mongolia Plateau in north China. As one of four branches entering Dalai Nur Lake in the Hexigten Grasslands nature reserve, this is the 17-km-long Haolai River.

The Hualai River (also known as the Haolai River) in Inner Mongolia, China, is widely recognized as the thinnest or narrowest river in the world. Stretching approximately 17 kilometers across the Hexigten Grasslands, this remarkable waterway has an average width of just 15 centimeters (about 6 inches). At its absolute narrowest point, it is a mere 4 centimeters (1.5 inches) wide, making it easy to cross with a single step. Despite its diminutive size, it is a true river with a steady, permanent flow fed by an underground spring, and it even supports small fish and aquatic plants. The river eventually empties into Dalai Nur Lake. It has been flowing for more than 10,000 years, and its name, "Haolai," appropriately translates to "the entrance to the throat" in the Mongolian language, referring to its constriction. While it looks like a mere trickle or a meadow crack, it possesses all the hydrological characteristics of a natural river, including a distinct basin and seasonal changes.