Rila (Bulgarian: Рила, pronounced [ˈriɫɐ]) is the highest mountain range of Bulgaria, the Balkan Peninsula, and Southeast Europe.

The mountain range has varied flora and fauna with a number of endemic and relict species and some of the best preserved forests in the country.

Musala is the fourth most isolated peak in continental Europe after Mont Blanc, Mount Elbrus and Galdhøpiggen raising at a distance of 810 km from the nearest point of the same elevation.

[4] Rila is a fault-block mountain and represents a crescent-shaped horst with two fault systems — concentric and radial.

Traces of these sediments are found in the Northwest Rila at an elevation of up to 1,900 m. The highest zones are made mainly of granite, and below are crystalline schists, whose compound minerals are sequentially deposited.

There are marbles and amphibolites formed in the Paleozoic over 250 million years ago and subsequently elevated during the Tertiary period.

In the lower parts, the average monthly speed varies from 1.2 to 2.5 m/s and in the middle height zone it ranges from 2.5 to 3.2 m/s.

The regime of the rivers of Rila is directly related to the elevation and about half of the water reserves in the mountain are at an elevation above 2,050 m. The main drainage divide in the Balkans separating the drainage basins of the Black Sea and the Aegean Sea passes through Rila's northern ridge, including the summit of Musala.

[10] Some of the Balkans' longest rivers originate from Rila, including the Maritsa, Iskar and Mesta, as well as several important tributaries of the Struma — Rilska, Dzherman and Blagoevgradska Bistritsa.

[27] There are abundant mineral springs that include the hottest one in South-eastern Europe at Sapareva Banya forming a geyser with a temperature of 101.4 °C.

[13][30] Their location is closely linked to the snowline during the last glacial period and most of them lie at elevations between 2,100 m and 2,500 m. Most lakes (28) are situated at elevations between 2,300 m and 2,350 m; there are 23 between 2,350 m and 2,400 m, 19 between 2,250 m and 2,300 m and 19 between 2,400 m and 2,450 m.[25][26] Their length varies between 800 m and 20 m, the width — between 375 m and 10 m, the area — between 1 m and 212 decares, the depth — between 0.5 m and 37.5 m. Most of them are between 2 m and 10 m deep and four reach depth of over 20 m.[25][26] The water is transparent as deep as 15 m. Most of the lakes are covered with ice during most of the year — from October to June.

[26] 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.

[36] Due to the difficult terrain, the forests of Rila are not much influenced by anthropogenic activities and their average age is above 100 years.

[37] Some Norway spruces and European silver firs reach height of 60 m.[38] The number of vascular plants includes about 1400 species registered only within the territory of Rila National Park,[22] 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.

[44] These include three relicts — boreal owl, Eurasian pygmy owl and Eurasian three-toed woodpecker, and species that require special conservation measures like short-toed snake eagle, golden eagle, peregrine falcon, black stork, Eurasian woodcock, western capercaillie, hazel grouse, rock partridge, grey-headed woodpecker, black woodpecker, white-throated dipper, wallcreeper and Alpine chough among others.

[46][47] The invertebrate fauna discovered so far includes 4186 species and is expected to rise to over 7000; of them 34 are endemic to Rila, 123 — to Bulgaria and another 123 — to the Balkans.

[50] Rila is a sparsely populated mountain range with most of the settlements located in the valleys at the foothills, inhabited by c. 250,000 people.

[52] There are a number of villages, including among others Govedartsi, Belchin, Madzhare, Kostenets, Pastra, Stob, Barakovo, Dobarsko, etc.

[36] Manufacturing industry is centred in Blagoevgrad, Dupnitsa, Samokov, Razlog and Belovo; the main sectors are food processing, machine building, pharmaceutical and paper mills.

Borovets, situated on the northern slopes at 9 km from Samokov, is the oldest winter resort in Bulgaria and the largest one in Rila.

[59][60] The top elevation is 2,560 m while the lowest is 1,300 m.[59] Over 36,000 foreign tourists have stayed in Borovets for the 2016/17 winter season spending an average of five nights.

[62][63][64][65] The Balmeken High Mountain Sports Complex is located at an elevation of 2,050 m in East Rila and is used for training, medical and biological research by athletes but also provides opportunities for family recreation.

[66] The mountain range was a favourite place of retreat for the Bulgarian monarchs Ferdinand I (r. 1887–1918) and his son Boris III (r. 1918–1943).

The palace of Tsarska Bistritsa was constructed between 1898 and 1914 above Borovets in the traditional Bulgarian National Revival style with several edifices and a park.

[68] There are 198 km primary and 363 km secondary hiking trails in Rila National Park, including E4 European long distance path that traverses it from west to south and E8 European long distance path that traverses it from north-west to south.

[71] The abundant mineral springs along the fault lines along the northern foothills of Rila favour health and spa tourism.

[76][77] The complex covers an area of 8,800 m2 and consists of a five-domed church, a defensive tower and monastic apartments encircling an inner yard.

[78] The Church of Saint Nicholas in Sapareva Banya is small medieval edifice, constructed anytime from the 11th to the 14th century.

It was built using red bricks and white mortar and is of a simple cross-in-square design, with a single nave and apse.

[79] The town of Samokov achieved economic prosperity during the 17–19 centuries due to production of iron and has a number of monuments, including churches, a convent, a 17th-century Ottoman drinking fountain and a museum of history.