The Ruhr area ('Ruhrgebiet') is named after the river that borders it to the south and is the largest urban area in Germany with over five million people. It is mostly known as a densely-populated industrial area. By 1850 there were almost 300 coal mines in operation in the Ruhr area. The coal was exported or processed in coking ovens into coke, used in blast furnaces, producing iron and steel. Because of the industrial significance, it had been a target from the start of the war, yet "the organized defences and the large amount of industrial pollutants produced a semi-permanent smog or industrial haze that hampered accurate bombing". During World War II, the industry and cities in the Ruhr area were heavily bombed. The combination of the lack of historic city centres, which were burned to ashes, and (air) pollution has given the area and the cities a bad reputation. Especially because it is so close to the Netherlands, I thought it would be an interesting area to visit for a little trip. I have spent three nights at a campsite on the Ruhr and visited six cities.

Essen is the ninth largest city in Germany and the second largest in the Ruhr region with a population of 580,000. Essen was founded around 845 and received its town charter and seal in 1244, when city walls were erected. At the end of the 16th century, many coal mines and the weapon industry began to flourish.

Essen's history has been closely intertwined with the Krupp family from the 16th century. In 1811, Friedrich Krupp founded Germany's first cast-steel factory in Essen and laid the cornerstone for what was to be the largest enterprise in Europe for a couple of decades. The weapon factories in Essen became so important that a sign facing the main railway station welcomed visitors Hitler and Mussolini to the "Armory of the Reich" (German: Waffenschmiede des Reiches) in 1937. The Krupp Works also were the main reason for the large population growth beginning in the mid-19th century.

Kray is an eastern district of Essen. It is one of the few districts which still has a fair amount of old buildings of the Gründerzeit.