I took a train ride along the Rhein from Heidelberg to Köln. The most beautiful stretch was from Mainz to Koblenz, where you see old castles along the river, and friendly little German towns. If I had more time, I would definitely like to do a river cruise.
You walk out of the train station in Köln, and you are in front of the huge gothic cathedral. It truly is magnificent. I had seen it once before in 1987 when I did some traveling while living in Salzburg. But this time it seemed even more huge and imposing. Here is a photo of the devastation of Köln in 1945, but the cathedral was spared.
I found a very nice vegan restaurant called Cafe Hibiskus. At the information center just across the cathedral, a woman gave me a booklet of all the vegan places in the city. No reason to think that it is hard to be vegan in Germany. Walking around was lovely, and I also crossed the bridge where people attach locks to signify their commitments to each other. Lots of shops and some parts reminded me of Stockholm, especially the main shopping street with the many H&Ms that seemed a lot like Drottninggatan.
I left the city with a fast train to Frankfurt, where I met my sister for one hour: I traveling to Stockholm, she to South Africa. What a pleasant nice time in Germany.