The fact that today's idyllic nature on the shores of Lake Baldeney was once used for coal mining can be seen here as hardly anywhere else in Essen. Near the Kampmann Bridge in Heisingen, the Geological Wall shows how the geological foundation of the Ruhr Region, because coal is clearly apparent in the profile. Besides the different layers of rock, there are also entrances to former mining tunnels and a collection of mining equipment. Visitors can also read informational panels to "dig deeper" into the site.