Big City Lights

On my flight back to Cologne (via Düsseldorf), the captain took a large curve. Due to that course deviation we flew across the Ruhrgebiet: Oberhausen - Gelsenkirchen - Essen. We almost flew over my hometown Velbert.

At night, the Ruhrgebiet looks so graceful. The thin spider-webs of civilization extend as far as the eye can see. It was awesome and such a kind welcome-home.

Only one thing made me think: the burning chimneys in the middle of the cities. Has anyone any idea what it could be? The coal mines of the Ruhrgebiet are almost closed?!