Car-free Siegtal for bikers/skaters 05-July (Duesseldorf)
Every year first Sunday of July, they block a section of Protected content along the valley of Sieg for all the motorized vehicles only for it to be used by bikers and skaters. Reportedly thousands visit every year to have fun on this day termed as "Fahrrad-Erlebnistag". This year, because of Deutsche Bahn's extensive construction work, a section of around about 50 km over Siegen up to Kirchen will be made available to non-motorized users. One can find many fun events take place along the way like open air music concerts, summer fests. It's going to be my first time.
For those interested, you can find more information here :-