Boybuloq (also known as Boy-Bulok and Boj-Bulok, , ) is a limestone cave in Uzbekistan, the deepest cave in Central Asia and all Asia except its western part. The cave is deep and long with the main entrance at an elevation of above sea level. It is situated at the edge of Baisuntau mountain ridge, the southern spur of the Gissar Range, in the southeast of the country. The nearest village is Dehibolo (Дюйбало in Russian), to the northeast of Boysun.
The cave developed in the covered karst of Upper and Middle Jurassic limestones, in monoclinal strata, in the preserved wing of an anticline. The thickness of limestone strata is 200–350 meters. Contrary to most limestone caves, it was not formed by water precipitation penetrating from the surface, but, as the soluble rock is covered by insoluble strata, by condensation. Hence the cave consists mainly of very narrow passages which descend along the incident angle of strata, from time to time interrupted by vertical shafts, no deeper than , and ends with an impassable siphon.
It was explored by Russian cavers since 1984, in the framework of Ekaterinburg Speleo Club (SGS) and the Assoсiation of Speleologists of the Urals (ASU), with the participation of cavers from Italy, Great Britain, Slovakia, France, and Switzerland (in chronological order).
Naming After a period of rain—a rarity in an otherwise very arid mountain climate—a small stream began flowing from the cave's entrance. This phenomenon was referred to as boybuloq, a fusion of the words boy and buloq, meaning "rich spring" in the Uzbek and Tajik languages.
Early history
The cave was known to local people since ancient times, because from its entrance a stream of water flows down the slope of the otherwise-very-arid mountain landscape. In the winter, the village Dehibolo, at an elevation of (whose name translates to "the highest village"), is cut off by the snow; later in the summer the few springs, which provide water to residents, can dry up. In May 1970 Mustafo Zokirovič Holmominov (born 1917), a farmer from Dehibolo, departed on a 4-hour trek to the cave (8 km) with his son Hudojberdi (born 1955) on three donkeys. The cave was known to him; he had visited it several times before. The two reached the cave and Mustafo went into the cave to pray. After a crawl of about one hour, he reached a point close to the first shaft, where his kerosene lamp went out. In the darkness he missed the direction towards the entrance, and fell to his death into the abyss. Hudojberdi waited at the entrance for two days until the villagers from Dehibolo came and returned him home by force.
Young men from Dehibolo tried to find Mustafo in the cave on several occasions that summer and in the following years but to no avail. His remains were not discovered until 1985, during the first speleological exploration of the cave.
Exploration
After the discovery of Kiev Cave on the Kirk Tau plateau in Uzbekistan in 1972, 2340 m a. s. l., which was in the subsequent years explored to the depth of 990 m and was in the years 1977–1978 the deepest-known cave in the USSR, Russian speleologists from Yekaterinburg (SGS) in the late 1970s and early 1980s started to search for new deep caves in the wider area of the country. In May 1981 they discovered the Zindan cave (later renamed to Urals-Zenkov cave), 3100 m a. s. l., in the Ketmen'-Čapta ridge. Its spring at the elevation of 1300 m indicated the possibility of a very deep cave. In January 1983, the final depth of 565 m was reached, in a siphon too narrow to dive. Several expeditions in the summer 1983 were fruitless, while in 1984 a token SGS expedition to Hodja-Gur-Gur-Ata massif discovered a number of promising entrances.
During a larger expedition in 1985, a group of five expedition members was sent to Surkhan-Tau ridge to scout its surface for new caves. On the way, in the village Kurgancha, 1455 m a. s. l., they were told of a cave higher in the mountain, called Boybuloq, into which a villager from the highest settlement in Uzbekistan, the village Dehibolo, went in 1970 and never returned. They followed the stream bed and discovered the low cave entrance, at an elevation of 2647 m. The cave began with 7 meters of a crawl in liquid mud, with scattered stone supports, after which it was possible to stand up. A high-but-narrow meander followed, it slowly ascended for 600 meters in straight direction, to a height of 90 meters, where it turned down. Soon a 27-meter pit was reached and they discovered human bones at its bottom. They belonged to Mustafo Zokirovič Holmominov.
Boybuloq and most other caves in the area are a long sequence of tight passages which are difficult to pass, and where possibilities for help or rescue operations are very limited, as described by Sergej Kuklev, a member of the SGS team:
In the following years further expeditions took place: in 1986 the cave was deepened to −400 m, in 1987 to −500 m and the remains of Zokirov were returned to his family, in 1988 a siphon at −600 m was free-dived and also the barrier on the other side lowered so that the lake could be waded through, and a new branch of the cave was discovered – it continued to −900 m. In 1989 a combined Soviet-Italian team reached the terminal siphon at −1158 m, and managed to climb upwards to the point at an elevation of +156 m which gave the total cave depth of 1310 m. In 1990 a Soviet-British team managed to extend the New branch in the cave upwards to +222 m (total depth 1376 m). As can be seen from the above map, this international participation in discoveries was reflected in the naming of three substantial cave sections: the Italian, English, and Russian tunnels.
In 1991 lower levels of the New branch were discovered, and in 1992 an additional chimney upwards was climbed to +257 m, which gave the final cave depth of 1415 m. In 1995 a major collapse in the cave was dug through, in 1998 the diving of the siphon at −560 m was unsuccessful, and the spring Holtan-Čašma, where the water from the terminal cave siphon comes to light, was also dived. The spring is situated 130 m below the terminal cave siphon while the horizontal distance is 7 km, so the connecting passages are most likely submerged. In the next years the turmoil which followed the dissolution of the Soviet Union was unfavorable for caving expeditions and SGS cavers returned to Uzbekistan only in 2007, to Boybuloq, and expeditions followed almost every year. New passages in Boybuloq were discovered and explored, yet the cave depth remained the same. Diving in the Holtan-Čašma spring was resumed in 2014, 2015 and 2016, when, at a horizontal distance of 170 m and depth of 18 m, a lenticular grotto was reached with narrow, downward-extending slots, too narrow to pass.
During the 2021 SGS and ASU expedition, a survey team mapped the upwards-extending tunnels in the New branch of the cave, explored in 2016. Survey data showed that the highest point achieved, where the tunnel narrows into an as-yet impassable hole with very strong air current, is situated 272 m above the cave entrance. Boybuloq's amplitude changed from 1415 m, achieved in 1992, to 1430 m, and its length increased to 15,212 m.
In 2022 a 20-member Russian expedition called Boybuloq 2022 took place in August, again organized in the framework of SGS and ASU, led by Vadim Loginov. It only operated in Boybuloq. The base camp was established at 2770 m a. s. l., 120 meters above the cave. The only goal was to explore any possibility of connecting the cave to Višnevskij. There were four working groups. The diving group of two explored three siphons. Two were too narrow to pass, while they successfully dived through the third. Upstream, a large tunnel followed; one of the two divers explored a short distance and returned. Exploration of this part of the cave was postponed, since a lot of equipment is required for climbing after the siphons. The scouting group, also of two, checked the side tunnels and meanders in the vicinity. They found several smaller tunnels, which all ended in narrows. No draught in the direction of Višnevskij was found. The climbing group, again of two, explored the upper floors of the cave. They discovered several closed loops, of a chimney which led to a horizontal tunnel, ending with a pit that brought them down into the already-known part of the cave. At the end of expedition they climbed a 170-meter-high chimney, wide enough, which continued with a tunnel, presumably leading in the direction of the Višnevskij cave. Due to the lack of time they returned. The mining team of four was widening the narrows in the projected direction to Višnevskij cave. They advanced around 20 meters; there was no draught to follow. The cave depth did not change; around 1 km of new tunnels were explored; no survey was made.
In 2023 a large, 33-member expedition, Russian with one participant from Taiwan and one from the Czech Republic, worked in August, in the same arrangement as in 2022. This year they operated in both caves, Boybuloq and Višnevskij. In Boybuloq the mining group worked at the closest point to Višnevskij, advancing 20 meters but finding no draught. The climbing group followed the tunnels and chimneys in the direction of Višnevskij. They discovered several new galleries; on top of the 170-meter chimney, the tunnel continued for 666 meters and ended with a collapse. Speleothem samples were collected in the cave Lunnaja (Moon cave, which runs above the tunnels of Višnevskij cave) to be analysed at the Department of Geosciences, at National Taiwan University. At the top of Boybuloq, in a tunnel 270 m above the cave entrance, a new underground camp was established from which a small group was expanding the narrow passage at the highest point of the cave, with a very strong air draft. They advanced 4 meters. Another group was working from the underground Camp Zero (approximately the same elevation as the Boybuloq entrance). They climbed a few steps and chimneys and in one of them discovered a narrow tunnel which continued upwards in the direction of the top of the Chulbair ridge, to the wall on its eastern side. They passed 1.5 km of the tunnel, and surveyed part of it. On the last day of the expedition they measured the altitude of the last point reached with an altimeter, considerably extending the amplitude of Boybuloq. The tunnel continues, but they had to return due to lack of time. After the expedition, Boybuloq had a new depth of 1517 meters and a length of 18.4 km.
The 11-member SGS and ASU expedition in August 2024, named Boybuloq 2024, the smallest since 2017, did not change the Boybuloq's depth or length but it discovered an important ice cave, Bear cave (Medvežja peščera) at an altitude of 3768 meters above sea level, 246 meters above the entrance to Višnevskij cave. The 35-member expedition in August 2025, one of the largest, also in the framework of SGS and ASU, named Asia 2025 as it also operated in the caves of Hodja-Gur-Gur-Ata ridge, managed to increase the depth slightly, to 1523 meters, going upwards from the point reached in 2023. They also made the survey of cave parts, discovered earlier and during this expedition, to obtain the new cave length of 19900 meters. Expedition worked in both caves, in Boybuloq and Višnevskij. On the last day of the expedition's work in Boybuloq the connection searching team discovered the most promising lead so far, with strong air current, and advanced 50 meters through the meander towards Višnevskij.
Višnevskij Cave