Gelsenkirchen (IPA: [gɛlzənˈkɪʁçən]) is a city in North Rhine-Westphalia, Germany. It is located in the northern part of the Ruhr area. Its population in 2006 was c. 267,000. Gelsenkirchen was first documented in 1150, but it remained a tiny village until the 19th century, when the Industrial Revolution led to the growth of the entire area. In 1840, when the mining of coal began, 6000 inhabitants lived in Gelsenkirchen; in 1900 the population had increased to 138,000. In the early 20th century Gelsenkirchen was the most important coal mining town in Europe. It was called the "city of a thousand fires", for the flames of mine gasses being flared during the nights. In 1928 Gelsenkirchen was merged with the adjoining cities of Buer and Horst. The city bore the name Gelsenkirchen-Buer, until it was renamed Gelsenkirchen in 1930. During the Nazi era Gelsenkirchen remained a centre of coal production and oil refining, and for this reason it was bombed by Allied air raids in World War II. During the war, it was the site of a women's subcamp of the Buchenwald concentration camp.Today in Gelsenkirchen there are no collieries any more and Gelsenkirchen is searching for a new image, having been hit for decades with one of the highest unemployment rates of Germany. Today Germany's largest solar power plant is located in the city. In Gelsenkirchen-Scholven there is a coal fired power station with the tallest chimneys in Germany (302 metres).