The water-filled sinkholes, many of them perfect circles, are the trademark of the unspoilt volcanic Eifel region in the Rhineland Palatinate uplands. At first glance, they look like lakes, but they are really a throwback to a volcanic eruption, one of many in the history of volcanic activity in the Eifel. The three Daun maars – the Weinfelder, Schalkenmehrener and Gemündener Maar – are among the most popular maars, also called the ‘eyes of the Eifel’. There are plenty of opportunities for walks in the unique natural landscape surrounding the maars. We have put together some circular routes.