If you visit Cologne during the holidays, shop at the Christmas markets and visit the Cathedral.

The church is amazing. If a mass is going on, you will have to wait, but it is well worth it to see the church. There is also a stairway to the very top of the Dom, but you could find it exhausting even if you are in very good shape. The stairs are so steep and so slim, it can be dangerous if you're not careful. Once you reach the top, you'll find lots of grafitti left by other visitors, and you may find the view was not quite worth that arduous climb! So, do it if you're healthy and curious, but be realistic about your expectations.

The Dom is lovely and breathtaking, but may be better from level ground.