Renting and riding bikes around Cologne is a great way to get out and explore the area. There are paved bike-only paths and bike lanes throughout the city, along the Rhine River and out in the countryside.
Radstation is a good place to rent. They have a wide selection of comfortable, modern bikes such as city bikes, ebikes, and tandem bikes.
To rent they just require an ID and prepayment. A city bike starts at €2 per hour or €12 per day and prices go up from there. Radstation is located at Map Location: 50.942544, 6.96009 and also Map Location: 50.936524, 6.962807 .