Hidden in the forest are reminders of border history: the path leads through the middle of the former Westwall, which was intended to secure the border between Germany and Belgium. Now overgrown with moss, the humped line of reinforced concrete is easy to walk through and fulfills a peaceful function as an ecological niche. Along the way, rows of gnarled beech trees trace the course of the Landgraben. They are a remnant of Aachen's city fortifications, which were secured by an overgrown hedge. The hedge has not been cut for around 100 years, the trees have sprouted and formed the often bizarre-looking harp shapes of today. The Cyclopean stones, which have been resting here for millions of years, care little for the border. Scientifically speaking, they date back to a time when the border lay on the sandy shores of the Cretaceous Sea. Other explanations are dazzling and varied, but whether they were brought here by giant cyclopes, were a place of worship or whether the devil lost them from his sandbag, the idyllic spot is always worth a stop.