Zănoaga Mare Lake, Retezat National Park

Lake Zănoaga Mare is a glacial lake located in the Retezat Mountains, part of the Retezat-Godeanu mountain group of the Southern Carpathians. It is the deepest lake of its type in the country, its maximum depth being 29 m. It is a lake formed in a glacial cirque.

Situated in the glacial caldera of the Judelui, on the southern slope of the Sesele mountain, at an altitude of 1997 m, the lake has a circular shape, with a maximum length and width of 360 and 260 m respectively, and a perimeter of 875 m, thus covering an area of 6.0 ha and a water volume of 693000 m3.

Pleistocene Quaternary glaciations in the Carpathians left numerous traces: calderas, hanging valleys, U-shaped and stepped valleys, moraines and glacial lakes. Such traces, which have been attributed to the last two glaciations, Riss and Wurm, can be found in the Rodnei Mountains, the Călimani Mountains, the Bucegi Mountains, the Făgăraș Mountains, the Iezer-Păpușa Mountains, the Parîng Mountains, the Retezat Mountains, the Godeanu Mountains and the Țarcu Mountains.

In general, the lakes were carved by glaciers into the hard rock of mountain massifs, at the mouths of valleys or even in valleys, forming glacial cirque and valley lakes. Most formed in the irregularities created by the frontal and lateral moraines of the caldera glaciation.

Circus lakes have the largest share, they are small in area and shallow, but cases with surprising depths are also known. Glacial cirques are somewhat circular in shape and are found close to the mountain ridge at the mouth of valleys. Snow accumulated and turned to ice at the valley mouths by undercutting has formed depressions bounded at the bottom by glacial thresholds. This type of lake is found in every mountain range that has been affected by glaciation: in the Rodnei Mountains, the Făgăraș Mountains and the Retezat Mountains.

Circus lakes are not only found isolated at the mouth of a valley. In some larger, branching upper basins, suites of circuses have developed, called circus complexes. Another form found in glacial relief is that of stepped cirques, developed on the same valley axis as a result of the succession of glacial phases.