Take a walk or dive into one of the Eifel's many "maars", natural lakes that lie in an inactive volcano funnel.
The name "maar" is derived from the Latin word "mare" (= sea) and applies to the type of funnel-shaped volcano created by eruptions of water vapor, which is "blown" into the landscape and often present in the form of a bowl.
In total, more than 70 "maar" volcanoes have been recorded in the region - only twelve "maars" are still filled with water today, the others having already silted up.
In summer, you can even swim in some maars: Meerfelder Maar, Pulvermaar, Schalkenmehrener and Gemündener Maar.
For more information, check out this link to the official website: Link to the website