If you are just passing Oberbilker Markt via one of the main roads, you might not be aware that hiding behind all those fancy office buildings, there's a park.
In the rectangle created by Kölner Str., Werdener Str. and Moskauer Str., surrounded by modern buildings, there is a park. You won’t notice it if you drive past, but there are several tiny access roads and entrances that allow you to enter this rather geometrical designed green space. The park is rather narrow and long with a boulevard around it and an artificial lake in the middle.
The areal used to be an industrial site, but production ended in the 1970ies and starting in the 1990ies, new offices and business buildings were constructed, with this curious patch of green right in the middle. People spend their lunch breaks there, play soccer, go running or just hang out in the sunshine when the weather is nice.
The park is certainly not the first choice for nature-lovers, it does have a rather artificial and constructed vibe to it (but then it is still relatively new anyway), but it’s great if you need a break from urban exploring and there’s also loads of interesting architecture surrounding it that’s just waiting for you and your camera.
To get there, take a tube to „Moskauer Straße“ and you’re right there. If you get out at „Oberbilker Markt“, there is a passage way right on the corner Kölner Str./Werdener Str.
http://www.duesseldorf.de/stadtgruen/park/ihz_park.shtml (German only, sorry!)