The City Lake covers an area of 43.6 ha. It is a shallow reservoir. The maximum depth is only 5.6 m. The lake's waters are class III clean. The City Lake has two other names: Trzcińskie - due to the place where it is located, and Trzygłowskie - this name is explained by the legend. It claims that a long time ago a Slavic tribe, called Licikawikami, lived here. The god of the tribe was Trzygław, who warned of dangers by appearing at the lake and scaring enemies. The locals paid tribute to him in the temple on the island where his wooden statue was located. When Christianity reached these lands, Trzygław left the reservoir, leaving a permanent mark in the form of a characteristic shoreline resembling three heads of an idol. This legend is also popular in other parts of Western Pomerania.
On the shores of the lake, on one of the peninsulas, there is the building of the Spa House. At the end of the 19th century, local physician Dr. Boding discovered layers of peloid peat with a high content of minerals, especially iron and sulfur. Thanks to his initiative, the first bathing area was established, and then a medical facility. Sick people from all over Europe came here, and the city received the title: Zdrój. After World War II, due to the nearby location of the Soviet military airport in Chojna, the treatment facility was closed. Only the name of the town remained after the spa.