The Trail of the Eagles' Nests (Polish: Szlak Orlich Gniazd) of south-western Poland, is a marked trail, named after a chain of 25 medieval castles which the trail passes by, between Częstochowa and Kraków. (wiki:
I recommend everybody to see it. There is even organized race in July to which everybody can join transjura.pl
I recommend everybody to see it. There is even organized race in July to which everybody can join transjura.pl