Tbilisi Reservoir (Tbilisi Sea) spreads on 11.8 km in the Eastern part of the city. It was opened in 1951 on the site of salty ponds of Avlabari, Ilguniani and Kukia. It is presumed that these three lakes were located in the ancient riverbed of river Mtkvari. The length of the pond is 8,75 km, the longest segment of width is 1,85 km, surface area – 11,6 sq.km, the maximum depth – 45 m. It is fed by waters of river Aragvi and Iori. Its waters are used for irrigation, water supply of Tbilisi, cultivation of fish, water sports. In various seasons of the year the water temperature in the reservoir of Tbilisi is characterized by rather big swings (average 18 degrees centigrade). True, the surface of the reservoir has no ice formation in winter, but the bank or a thin strip still goes icy. In July and August water warms up to 26 degrees and attracts a lot of visitors. In 2007, at the expense of Tianeti, Mtskheta and Sagarejo Forestry, part of lands of Didgori Experimental Model Forestry Foundation and Saguramo State Sanctuary, Tbilisi National Park founded in 1975 and called the lungs of the city, was revived and expanded. The purpose of foundation of this Park is protection of rare species of plants in the central part of Eastern Georgia and forest ecosystems typical for this territory, preservation of biological and landscape variety as well as furtherance of ecological safety and development of recreational, ecological tourism and educational activities in natural conditions. Tbilisi National Park is important from tourism expansion viewpoint as well. Protected territory is located in proximity of two important Georgian towns – Mtskheta and Tbilisi, and directly borders the masterpiece of the VI century Georgian architecture – Jvari of Mtskheta, from where magnificent panoramic view of the town of Mtskheta opens up.