Rila is a mountain range in southwestern Bulgaria and the highest mountain range of Bulgaria and the Balkans, with its highest peak being Musala at 2,925 m. The massif is also the sixth highest mountain in Europe (when each mountain is represented by its highest peak only), coming after the Caucasus, the Alps, Sierra Nevada, the Pyrenees and Mount Etna. The larger part of the mountain is occupied by the Rila National Park.
The name Rila is allegedly of Thracian origin and is thought to mean "well-watered mountain", owing to Rila's abundance of glacial lakes (about 200) and hot springs in the faulty areas. Some of the Balkans' longest and deepest rivers originate from Rila, including the Maritsa, the Iskar and the Mesta. Culturally, Rila is famous for the Rila Monastery, Bulgaria's largest and most important monastery founded in the 10th century by Saint John of Rila.
Rila is a dome-shaped horst mountain, part of the Balkans' oldest land, the Macedo-Thracian Massif. It was formed by granite and gneiss rocks and crystal schists during the Paleozoic (250,000,000 years ago), with Rila's alpine relief being formed later, 10-12,000 years ago, after the W?rm glaciation, when the snow line was at 2,100 m above sea level. Above this line glaciers radically changed the existing relief, creating deep cirques, sharp pyramid-shaped peaks, rock pinnacles, various valleys, moraines and other typical glacial formations.
Rila has an area of 2,400 km?. The dome of the mountain rises over the surrounding mountain valleys, with the Borovets Saddle (1,305 m) connecting the main Musala Ridge with the Shipchan and Shumnitsa ridges that connect to the Ihtiman Sredna Gora mountains through the Gate of Trajan pass. The Yundola Saddle (1,375 m) and the Abraham Saddle (1,295 m) link Rila with the Rhodopes to the east, while the connection with Pirin is the Predel Saddle (1,140 m), the one with Verila being the Klisura Saddle (1,025 m). The climate is typically mountain, with 2,000 mm of precipitation on Musala yearly, 80% of which of snow. The lowest average temperature on Musala ever measured in February is –11.6°C and the absolute minimum is -31.2°C. An average temperature for August is 5.4°C, the maximum being 18.7°C.