Did you know that in Wągrowiec in Poland there is an unusual phenomenon called bifurcation? Here, two small rivers, Wełna and Nielba, cross each other at a right angle without mixing with each other and continue to flow in their own currents. The Nielba River flows into Wełna, their waters swirl, and then the waters of each continue to flow along its bed. This unusual phenomenon is the result of human activity and is a consequence of drainage works carried out in 1830. It is the only phenomenon of its kind in Europe and one of only two in the world.