Ekaterinburg Speleo Club (SGS) (from Sverdlovskaja Gorodskaja Speleosekcija;[a] Свердловская Городская Спелеосекция – СГС), founded in 1961,[1] is a Russian, non-profit speleological organization dedicated to the exploration, research, and conservation of caves.

[2][3][4][5][6][7] In summer 1961 three hikers from Ekaterinburg, Jurij Lobanov, Nikolaj Lizunov, and Anatolij Vagapov wanted to cross the Ural Mountain ridge and to raft down the Višera river.

In the autumn of 1961, a team was formed, two substantial caves on the Serga river were discovered and SGS, speleo section of the Sverdlovsk city tourist club established.

Wire ladders were unsuitable for the descent and ascent in vertical sections of ever deeper caves, and the application of the single rope technique lagged behind because of stagnant, slow communication with the West.

At the end of the decade, technical problems were solved, SGS teams participated in expeditions to the main focus of Soviet speleology of the time, to the deep caves in the Western Caucasus, in Russia, and in Abkhazia, on Alek and Arabika massifs.

[11] In 1980 6 small teams of 4 people were sent to different mountain karst areas of the USSR: to Kazakhstan, to Pamir in Tajikistan, to Turkmenistan, and to Uzbekistan, with modest results.

The ridges here have an unusual structure: an almost vertical northeastern side and a gentle southwestern one, made of several different rock strata, including a covered limestone layer, 200–350 meters thick.

[12][1] An expedition led by Aleksandr Ryžkov discovered the Zindan cave in May 1981, 3100 m a. s. l., with springs at an altitude of 1300 m.[5] In January 1983 the final depth of 565 m was reached, in the siphon too narrow to dive.

[17] Below the 27-meter shaft, they discovered human remains, of Mustafaqul Zakirov, a teacher from Dehibolo who visited the cave, four hours away on foot, several times before.

All the (tiny) streams flowing in different directions in Boybuloq are, apparently, of condensation origin, since the floods the cavers observed on the surface do not reach the lower horizons of the cave.

[23] There are three ridges in the south-western spurs of the Gissar Range, part of the Tian Shan mountain chain, to the west of Baysun: Ketmen-Chapty, Hodja-Gur-Gur-Ata, and Chul-Bair.

In the summer of 1984 a small expedition of 9 people, led by Viktor Dianov, nevertheless departed to Uzbekistan, to try to open up new caves in the sinkholes near Zindan.

[24] After several days without success two members of the team, Sergej Matrënin and Igor' Belokrys, asked Dianov to depart to the Hodja-Gur-Gur-Ata ridge on the northeastern horizon, topped at 3700 m by very distinctive precipitous mountain wall, with a karst baseline defined by the Machai spring at an altitude of 1400 m.[18][25] Just for a few days to check the stories about "terribly deep caves" there, heard on the Baysun bazaar.

During the expeditions from 1986 to 1988 Emma Lobanova was marking the cave entrances in the up to 400 m high wall below the crest of the ridge, labeling them as R (for a reference point) and a number, for the distance in meters from Katataš, the towering rock outcrop at the far south, divided by 100.

Towards the end of the 1980s Soviet Union began to open up, under the leadership of Mihail Gorbačev movements such as perestrojka and especially glasnost led to the establishment of contacts with Western cavers.

One such instance involved Tullio Bernabei, a councilor of the Italian Speleological Society and Aleksandr Višnevskij, a senior member of SGS and expedition organizer.

[19][25][27] Unlike previous caves in the area, mainly composed of very tight meanders, Dark Star was wider, a large tunnel with lakes.

[28] As already mentioned in the previous chapter, the regional tensions after the dissolution of the Soviet Union, which never completely subsided,[29] civil war in Afghanistan and its aftermath exploration at the ridge virtually stopped.

A reconnaissance expedition by cavers from Krasnojarsk to the plateau on top of the ridge in 1996 discovered several promising entrances with strong air draft.

1500 m of new large tunnels were discovered, a new entrance, Vino rosso, the cave also connected to Iževskaja, which enabled easier access to deeper parts of Dark Star.

[25][31] In 2012 SGS, with the support of the Association of Cavers of the Urals, launched the largest expedition so far, with 29 participants from Russia, Italy, Spain, China, and Germany of which 10 were girls, very skillful in cave survey.

In the first one cavers needed 3 days to break through the ice-blocked tunnel but discovered new parts which ended in the mountain wall, with a new, easier cave entrance.

They also discovered around 40 m high waterfall at a depth of 750 m.[36][37] Previous achievements attracted the largest ever SGS expedition to Hodja-Gur-Gur-Ata in 2014, of 31 people from 6 countries which included a National Geographic photo team.

[38][2] A team of 4 set up camp on the ridge plateau, at an altitude of 3700 m. They surveyed a surface trek from above the Red dwarf entrance to the bottom of Dark Star.

They found several possible cave entrances, all located 30–50 m below the crest of the wall, and the most promising proved to be the one marked as ČB-15 (Chul-Bair 15), at an elevation of 3522 m, 25 m below the top of the ridge.

In the cave two new camps were set up, at −350 m and −600 m. Close to the latter, in a side tributary which continued in the ascending direction, a small gallery, a hint of a possible link with Boybuloq, was discovered.

In the canyon which leads to Boybuloq, dinosaur footprints were found, while in the New branch of this cave a new survey was made to better estimate the connecting point with Višnevskij.

Veezhay) is a river in the extreme north of Sverdlovsk Oblast, flowing east, a right tributary of Lozva, in a mostly uninhabited land of taiga, subarctic coniferous forest.

[1] Since the 1970s the main purpose of SGS was to explore the great caves, in the beginning of the Western Caucasus, from the 1980s in Central Asia, where a world depth record could be reached.

[57] The formation of many caves is associated with the underground flow of the river, they often contain anomalously large halls (up to 80 m in diameter), caused by a very thick layer of limestone.