Zagreb's Cathedral of Assumption of the Blessed Virgin Mary is a great example of Gothic architecture. The first structure was completed in 1217, but underwent several reconstructions (due to a Tatar invasion and an earthquake) and additions before it became the beauty we see today. Some of the fortifications that were built to keep the Ottomans at bay still stand, as you can see in the stone tower below:
The detail above the entrance is simply exquisite, and had it not been for the freezing, damp February weather, I would have been tempted to sketch some of it— though lately it seems it takes a lot for me to get out a pencil and sketchbook. I'm not allowing myself a new book until I finish the one I have completely.