Trail of the Eagles' Nests
The Trail of the Eagles' Nests (Polish: Szlak Orlich Gniazd) of south-western Poland, is a marked trail along a chain of 25 medieval castles between Częstochowa and Kraków. The Trail of the Eagles' Nests was first marked by Kazimierz Sosnowski.
Source: Wikipedia — Trail of the Eagles' Nests (CC BY-SA 4.0)