Kłecko Hillfort - Credit: Wikimedia Commons
Kłecko Hillfort (Grodzisko Barbara) is an early medieval gord dating back to the formation of the Polish state in the 10th century, located between the Gorzuchowskie and Kłeckie lakes on the Gniezno-Wągrowiec road. The gord takes the form of a hillfort of an oval shape with preserved dimensions of about 40 x 35 m. Read more on Wikipedia
Source: en.wikipedia.org