I visited the Kölner Dom (aka Cologne Cathedral) in Köln with Julian Münster, an old hockey friend of mine. I went again the morning after and climbed to the top. For future reference, I suggest leaving your luggage behind before deciding to embark on climbing the staircase :/
We also headed to the Gaffel brewery to try the local brew called “Kölsch”, a slightly strange beer which is traditionally served in little 200 mL glasses.