Hello. I'm from Canada and I visited Cologne Cathedral twice, once in 1989 and again during the World Youth Day event in August 2005. The cathedral is impressive both on the outside and inside. Architecturally, it is a classic, complete Gothic cathedral through and through. Yes, the exterior looks dirty, but the dark grit is mostly likely due to the carpet bombing of the city during the Second World War (which explains why the rest of the city looks fairly modern). I was surprised to learn in university that the cathedral was struck by bombs several times by the allies. Fortunately, the Germans removed and safely stored the stained glass windows in anticipation of damage, until after the war. And thankfully, the cathedral was not severely damaged. So I imagine that one day, the exterior will be cleaned up - an enormous undertaking. My greatest joy is looking at beautiful stained glass windows. They are outstanding. I did not see the new window that was installed later in 2007 - it's contemporary, but fairly uninspiring and does not fit in with the rest of the windows. I think there must have been an artist