Blue Lakes

The Blue Lakes are oxbows of the Kazanka river complicated by karst sinkholes that opened here about two hundred years ago. Fed by groundwater, they return up to six hundred litres per second to the river; in summer this water cools the Kazanka noticeably, in winter it warms it, keeping ice from forming downstream. The first description was made in 1829 by Karl Fuchs, rector of Kazan University and local historian. The Big Blue Lake hides two funnels — the Bolshaya and Malaya Puchina: eighteen and six metres deep, with gypsum springs gushing up to 250 litres per second on the bottom of the larger one. The water barely changes temperature: five to seven degrees in summer, three to four in winter. Because of its mineralisation and a lens effect, depth is deceiving: the lake looks shallow while staying deep. The name comes from the blue silt muds on the bottom; the water's colour shifts from azure to black, and in severe frosts the lakes steam with local mist. Since 1972 the area has been a protected natural monument, since 1994 a reserve of 1,910 hectares; the water and muds have long been famed as healing for the skin, and the nearby sanatorium draws on them too.