Cologne
DE
Cologne's Christmas markets occupy several distinct locations; the cathedral market is on Roncalliplatz.
A Christmas visit to Cologne involves several separate markets, not one citywide event with a single timetable. The Cathedral Christmas Market takes place on Roncalliplatz, immediately beside Cologne Cathedral.
Use the cathedral market as a specific starting point and check other organisers separately before adding more stops. A market's opening date, a public-holiday closure and the opening hours of the cathedral itself are different pieces of information.
Source: Cathedral market organiser.