The historic exterior green belt that runs around to Cologne, is an essential element of the unique citywide greenery system of the city of Cologne. Approximately 90 years after the start of the first construction work to a convertible, from surrounding the city green belt shows towards an intensely used recreational area for the population of Cologne, which simultaneously satisfies valuable ecological and climatological features. Sponsored by the Cologne Green Foundation app shows the 63 km long road through the belt in the left as well as right bank.