For O I shall go for Oybin. Oybin is a municipality in the district Görlitz, in Saxony, Germany, located very close to the border of the Czech Republic. (Wikipedia)
We went over a decade ago, travelling from Zittau to Oybin on a narrow gauge railway which I had found out about before we travelled – even got an idea of the timetable from the internet! The reason for the trip was to see the romantic ruins of the medieval monastery there, which apparently were much painted by the likes of Caspar David Friedrich….