Take it to Church

1
Check into the Hopper St. Josef, and take some time to learn about the history of the monastery-turned hotel before moving onto your old city exploration.
2
Head into the Altstadt to the Kölner Dom, the cathedral-to-end-all-cathedrals. If you would like to attend one of the services, there are a number of morning and evening masses offered in German.
3
After church, take in the majestic Rhine from the Höhenzollernbücke before launching into a walking tour of the city's 12 Romanesque churches, which you may just be able to fit into one long day.
4

Break for lunch at Habibi, a stone's throw from St. Mauritius, and sample some of the city's best Middle Eastern bites.

5
If you have been sufficiently stunned by medieval architecture, make a pit-stop at the Archäologische Zone, for a peek at an ancient Roman sewer system and praetorium.
6
Additionally or alternatively, discover the NS-Dokumentationszentruzm, one of the few historical sites left untouched by bombings during the war and preserves a record of war atrocities inside the former Gestapo headquarters.
7
For dinner, splurge on fine dining inside the converted water tower that is the Hotel im Wasserturm before strolling back to St. Josef.