Varna lake is the largest and deepest estuary lake oblong on the territory of the Bulgarian coast. The lake area – 17 sq km, with a depth ranging from 9, 5 to 19 meters. The origin of this basin is tectonic.

Formed it from the mouth of Provadiya river, and from the Black sea, the lake separates the two-kilometer-long sandy strip, which increases regularly. The southern coast is steep and high, while the North – sloping. The lake bottom is covered by a thick layer of silt, in some places reaching 30 meters. In addition, the deepest places of the bottom is covered with sulphurous mud black. It is used in order to mud, dirt Varna lake is very plastic and heat capacity, which enhances its medicinal properties.

The lake temperature and the level of salinity significantly influenced by incoming seawater. In the spring the salinity at the surface decreases and increases in summer-autumn period. In connection with a predominance of salt water over fresh water, the lake is home to the only marine fish species.

Surface water is sometimes heated to 25 °C. the Average annual surface temperature of about 14 °C, at the bottom, the water is heated by no more than +8 °C.

It is known that the area around the lake was inhabited even in ancient times, as evidenced by traces of vanished civilizations. On the banks of Varna lake, archaeologists found a pile dwellings, flint tools and canoes. It is also noteworthy that on the North side of the lake, in the modern industrial zone of Varna, in 1919, was accidentally found the famous necropolis excavations where carried out so far. In addition, with one of the elevated lake views of the ruins of the Basilica of the period of the Genoese colony.