is Okoto, one of the Seven Rila Lakes with a depth of 37.5 m; the highest is Ledeno at an elevation of 2,709 m; the lowest is Suho at 2,045 m. The most important lake groups are the Seven Rila Lakes (seven lakes), Musala Lakes (seven), Marichini Lakes (seven), Urdini Lakes (six), Malyovishki Lakes (three), Elenski Lakes (three), Chanakgyolski Lakes (two), Vapski Lakes (two), etc. Nature The vegetation is determined by the elevation. At the lowest portions there are xerothermal oak forests dominated by Hungarian oak (Quercus frainetto), pubescent oak (Quercus pubescens) and Austrian oak (Quercus cerris) with some Mediterranean cenosis of cade juniper (Juniperus oxycedrus) and scorpion senna (Hippocrepis emerus). Higher in the mountain up to 1,300 m the deciduous forests are primarily of sessile oak (Quercus petraea) with smaller participation of European hop-hornbeam (Ostrya carpinifolia), common hornbean (Carpinus betulus), Heldreich's maple (Acer heldreichii), Balkan maple (Acer hyrcanum) and European ash (Fraxinus excelsior); the zone between 1,300 m and 1,600 m is dominated by European beech (Fagus sylvatica), at places mixed with European silver fir (Abies alba). The endemic Rila oak (Quercus protoroburoides) inhabits only the Rilska River valley. The forests of coniferous zone between 1,600 m and 2,100 m consist of primarily of Norway spruce (Picea abies), Macedonian pine (Pinus peuce) и Scots pine (Pinus sylvestris). The sub-Alpine zone up to 2,500 m is covered by dwarf mountain pine (Pinus mugo) and common juniper (Juniperus communis) formations mixed with green alder (Alnus viridis) at wetter localities and Rhododendron myrtifolium in East Rila. The alpine line is covered with grass, moss, lichen, rare flowers, dwarf willows such as Salix herbacea, Salix retusa and Salix reticulata, etc. Due to the difficult terrain, the forests of Rila are not much influenced by anthropogenic activities and their average age is above 100 years. Some Norway spruces and European silver firs reach height of 60 m. The number of vascular plants includes about 1400 species registered only within the territory of Rila National Park, of them 34 are endemic to Bulgaria, including three restricted to Rila, and 89 — to the Balkans; 31 are Tertiary or pre-glacial relicts and 104 are glacial relicts. Notable Bulgarian endemic species include Rila primrose (Primula deorum) and rhapontic rhubarb (Rheum rhaponticum); taxa restricted to the Balkans include Bulgarian avens (Geum bulgaricum), yellow columbine (Aquilegia aurea), Bulgarian gentian (Gentianella bulgarica), Balkanian butterwort (Pinguicula balcanica), Crocus veluchensis, Dianthus microlepis,