Blankenheim - source of the Ahr - Eifel Museum - Viaduct Onerahreck - Freilinger See difficulty: medium, duration approx. 3 hours, ascent: 343m, descent: 361m; the first stage is already impressive with its wealth of natural monuments and cultural treasures. The source of the Ahr in Blankenheim forms the starting point of the first stage. Past the Eifel Museum and the Römerstrasse information center, you stroll through alleys, along the Schwanenweiher, following the upper course of the Ahr. Then it goes through the railway underpass. Now it is getting more challenging and you are hiking steeply uphill. Through thick beech wood you come to the plateau of the Birker mountain. Spectacular views of the southern Eifel heights reward the climb. Passing fields, over quiet forest paths of the 484 meter high Bohrsberg you reach the shores of the Freilinger lake.