Hello! I wanted to share a very interesting article I saw today, about the little known history of the Knights Templar in Poland:
https://www.cnn.com/travel/article/knights-templar-holy-grail-poland/index.html
During the middle ages, the Kingdom of Poland invited the Knights Templar to settle the western reaches of the Kingdom (what's now the Polish-German border). The result is a string of Knights Templar churches, chapels, and fortifications from Pomerania in the north down to Silesia in the south, following the Oder river.
I'll admit that I was unaware of the existence of these sites, but it looks like a fantastic roadtrip itinerary through some of the lesser known parts of Poland, along the German border. The local legend is after the Knights were excommunicated and expelled in the 14th century, they hid the Holy Grail in a lake close to the town of Myślibórz. Though that's sounds like some great marketing from the local tourism office haha!