Source of WonderWhen the Pontarlier factory caught fire in 1901, the Loue River turned absinthe green. This surprising phenomenon revealed the link between the Doubs and Loue Rivers.The site provides a spectacular natural show. Water from a subterranean river makes a deafening noise as it falls from high cliffs. The flow is impressive, especially after heavy rains or at the end of winter. Not surprisingly, this natural force has been harnessed to produce hydraulic energy.