The disappearance of the Danube is described in every tourist guide and, although the phenomenon is no longer a mystery, it still raises the curiosity of cycle tourists. The Danube disappears at Immendingen, in a meander far from EuroVelo 6, so I have to get off my bike and walk the kilometre that separates me from this curious spot. The Danube’s disappearance is caused by the extreme porosity of the Jurassic rocks in this area, which allow the waters to percolate through the limestone and reappear twelve kilometres further downstream. Arriving at the designated spot, I couldn’t see anything untoward: far from disappearing, the Danube continued to flow joyously through the rich, green forest. A frustrated young Dutchman was paddling through the river, searching in vain for a sign of where the river was supposed to disappear. Heading back to the road, I came across the explanation on a notice board. In fact, the Danube’s disappearing act is intermittent, as it only soaks into the rock for about 155 days a year, when warm weather drastically reduces its flow rate. The day I arrived it had been raining heavily, as it had done for several of the previous days!