Gopło ' is a lake

Lake

A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...

 in Kuyavian-Pomeranian Voivodeship

Kuyavian-Pomeranian Voivodeship

-Transportation:Transportation infrastructure is of critical importance to the voivodeship's economy. Kuyavia-Pomerania is a major node point in the Polish transportation system. Railway lines from the South and East pass through Bydgoszcz in order to reach the major ports on the Baltic Sea...

, north-central Poland

Poland

Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...

, near the city of Gniezno

Gniezno

Gniezno is a city in central-western Poland, some 50 km east of Poznań, inhabited by about 70,000 people. One of the Piasts' chief cities, it was mentioned by 10th century A.D. sources as the capital of Piast Poland however the first capital of Piast realm was most likely Giecz built around...

. It gives its name to the protected area

Protected area

Protected areas are locations which receive protection because of their recognised natural, ecological and/or cultural values. There are several kinds of protected areas, which vary by level of protection depending on the enabling laws of each country or the regulations of the international...

 called Gopło Landscape Park.

In early Middle Ages, the shores of Lake Gopło were home to a West Slavic tribe of Goplanie. At the northern end of the lake stands the Mouse Tower of Kruszwica

Kruszwica

Kruszwica is a town in central Poland and is situated in the Kuyavian-Pomeranian Voivodeship , previously in Bydgoszcz Voivodeship .It has a population of 9,412 people .-History:...

. Its name derives from a legend of the corrupt Prince Popiel

Popiel

Prince Popiel was a legendary 9th century ruler of the West Slavic tribe of Goplans and Polans, the last member of the pre-Piast dynasty, the Popielids...

, whose fled to the tower from his rebelling population, and was devoured there by mice. Some historians and archaeologists consider the area the heart of the first state of the Polanie, the "founding" tribe of Poland.