One of the most memorable cultural sights in Cologne is the Cologne cathedral. Construction started in the 13th century and it took a couple of hundered years to fully complete the cathedral. It is truly a remarkable piece of arcitechture. The entrance is free and you can take photos. If you want to climb one of the two towers then you have to pay. We gladly payed and the sights from the ca. 300 m tall tower was breathtaking.