Bonn, the former capital of West Germany is located due south and easy to reach by train or Stadtbahn U-Bahn line 16 and 18.
Brühl, almost a suburb of Cologne, contains the Augustusburg Palace which has been placed on the UNESCO World Heritage List. The palace is one of the key works of Balthasar Neuman, and contains one of the finest Rococco interiors in the world, the highlight being the main staircase. Also in the grounds is the magnificent hunting Lodge of Falkenslust. Brühl can be easily reached by train in around 20 minutes from Cologne. The theme park of Phantasialand is also in Brühl.
Düsseldorf
Königswinter A small town reachable by train.
Ruhr Ruhrgebiet If you are interested in heavy industry this might be a worthwhile trip. It is located about 100 km north of Cologne. The region, which was the center of montan coal and steel industry in Germany, is going through a structural transformation and proudly presents its industrial past on the Industrial Heritage Trail (http://www.route-industri...).
Zülpich -- a small town southwest of Cologne dating from Roman times. It has a newly opened museum centered on Roman baths and bathing culture. It is also a gateway to the forested hills of the Eifel region.
