Time in Cologne

Yes, the lockers are big enough. If I recall rightly, it is the automated storage system. You know there is an AVIS location in the train station by the DB Travel Center (Reisezentrum). I am sure you can get a taxi at the nearby Dom Hotel, or at the very least, at the train station on the opposite side of the station from the main entrance.

One of the whole points of visiting Cologne is that the Dom is across the plaza from the Hauptbahnhof. You could hit it with a softball. I've spent five nights in Cologne, and haven't seen it all yet. But you won't be the first visitor to see the Dom, unwisely decide to skip paying for the Treasury below, and move on to the next town. As implied, there are a few car agencies within walking distance of the HBF and the Dom.

You didn't ask advice about the rest of the day, but are you planning to ride the KD boat within the most scenic part of the Rhine, Bingen to Boppard? A car doesn't make that impossible at all, but it does require thinking about it. Many travelers consider the view from a car far inferior to the KD boat ride. You have a long way to go, in perhaps business day traffic on the highway. Any castles in mind? See Rick's list of the best Rhine castles, free on the site, I think.

You can get to the cathedral directly from the train station. It's right at the back of the train station. We had a layover for about 1 1/2 hours and were afraid it wasn't enough time but we had enough time to have a coffee at Starbucks outside and watch the cathedral while we sat. We spent about 45 min in the cathedral and that was a lot, I thought. We took our carry on size luggage with us. But they do have storage for that size. That train station had a very helpful information center and we got some advice on station changes we needed to back later in the day. I believe that there were rental car kiosks in the station near that back entrance. It's very compact and efficient station, I thought.

Jenny

Thank you for your help.