Last time I went to Essen, I had a really good time. Perhaps thanks to the good weather, but the town also has some nice spots to offer!
You can begin with a walk around the Baldeney See and eat at the greek restaurant there. The villa Hügel has to be visited: the whole story of the famous Krupp family and the development of the steel industry is described.
Then you can go to the Industry culture heritage museum : Zeche Zollverein and discover the history and the machines of the UNESCO listed german industrial region.
A neighbor building is dedicated to the Red Dot museum, the label for design and ergonomics. I found it nice, even if I expected more special object with astonishing design. The exhibition presents more all day objects than unusual things: you probably will recognize your own objects among the exhibited pieces! It is also possible to see the awarded pieces online.