Of the about 100 Christian sites (churches, cathedrals, monasteries) on the List, only a few are related to Protestantism. The Luther memorials in Germany are the most prominent example of these. Roskilde Cathedral is another one: not so obvious maybe (it started out as a Catholic church), but the Reformation had a profound influence here. The interior was profoundly changed after the transition to Protestantism. In a way, its brick walls (already devised in the 1170s) add to the purity and austerity of the Reformation too.
Usually, I don't get too excited about visiting another Gothic cathedral, but I must admit that this one has something 'extra' that a spot in the Top 1000 world monuments seems to be deserved.
This 'extra' can be contributed to it being Protestant (as explained above), but also to all add-ons that were attached over the ages.
Each chapel has its own look, both inside and outside, and is an example of the fashionable architectural style during the period of its construction. One of the most beautiful of these, the Chapel of the Magi (1463), unfortunately, was closed for restoration when I visited. However, you can peek inside and admire its delicate mural paintings.