Cologne is the fourth largest city in Germany, famous for Cologne Cathedral, perfume, and the Rhine River. From the perspective of tourists, I think there are not many attractions that Cologne can visit, mainly concentrated near Cologne Central Station, about a day can be visited! The traffic part is not complicated, the main solution is to solve this train from the airport to the central, after arriving at Cologne Central Station, as long as you can walk to visit various attractions.