There are three holes in the ground on the Selma Plateau in the eastern Hajar Mountains. From above, they look unremarkable — circular openings in a flat, rocky surface, the kind of feature you’d step around without slowing your pace. The largest is maybe three metres wide.
Below those holes is the second largest cave chamber on Earth.
Majlis Al Jinn — Meeting Place of the Spirits in Arabic — has a floor area of 58,000 square metres and a ceiling that rises 120 metres above it. The Great Pyramid of Giza fits inside with room to spare. The temperature inside is a constant 20 degrees Celsius while the plateau above bakes at 40 degrees in summer. Sunlight pours through the three openings in beams that reach the cave floor 120 metres below, and the effect has been described, by every person who has stood inside it, as unlike anything they have seen before.
The Hajar mountain caves — Majlis Al Jinn, Al Hoota, the 7th Hole, Tahery, and dozens of others — are one of the least-known aspects of one of the least-known countries in the region. This guide covers them properly.
Hajar Mountain Caves at a Glance
- Most extraordinary: Majlis Al Jinn — 2nd largest cave chamber on Earth, requires abseiling 120m to enter
- Most accessible: Al Hoota Cave — the only developed show cave in Oman, guided tours daily
- Best adventure caving: 7th Hole Cave and Tahery Cave — technical caving through connected Hajar cave systems
- Most dramatic sinkhole: Bimmah Sinkhole — limestone collapse filled with turquoise water, accessible year-round
- Best for wildlife: Al Hoota Cave — blind cave fish found nowhere else on Earth, 100+ cave species
- Season: October to April for comfortable access. Caves stay around 20°C year-round.
Why the Hajar Mountains Are Full of Caves
The Hajar Mountains are limestone. That single fact explains everything that follows.
Limestone — calcium carbonate — is soluble in water. Rainwater absorbs carbon dioxide as it falls through the atmosphere, forming a weak carbonic acid. That mildly acidic water, percolating through cracks in limestone over millions of years, dissolves the rock — slowly at first, then faster as the passages widen, then faster still as the water table changes and air replaces water in the enlarged cavities. The result is karst — a landscape riddled with caves, sinkholes, and underground drainage systems that surface-level observation gives no indication of.
The Hajar Mountains are among the most extensive karst limestone formations in the Arabian Peninsula, and they have been uplifting and eroding for tens of millions of years. The Dammam Formation — the limestone layer in which most of the major Hajar caves formed — dates to the Eocene epoch, 40 to 50 million years ago, when this entire region was a warm, shallow sea. The shells and organisms that accumulated on that ancient seafloor became the rock that the caves now occupy.
Oman has over 1,000 documented caves and sinkholes. Most of the significant ones are in the Hajar Mountains. Most have never had a visitor who wasn’t a geologist.
Geological source: Majlis Al Jinn formed in Eocene-era limestone, 40–50 million years old. According to surveys, it is one of the largest natural cave chambers in the world, with a floor area of around 58,000 m² and a volume approaching 4 million m³.
The Caves of the Hajar Mountains
Majlis Al Jinn — The Second Largest Cave Chamber on Earth
In June 1983, Don Davidson and his wife Cheryl Jones discovered the entrance holes on the Selma Plateau during a caving expedition in the eastern Hajar Mountains. The entrances are named: Khoshilat Maqandeli (First Drop), Khoshilat Beya Al Hiyool (The Asterisk), and Khoshilat Mingod — Cheryl’s Drop, the deepest, at 158 metres — named after the woman who first identified its significance.
The single chamber beneath those three openings has a floor area of 58,000 square metres, a volume of 4 million cubic metres, and a ceiling that soars 120 metres above the cave floor. It is, by floor area, the second largest known cave chamber in the world, and the largest into which natural sunlight penetrates — the shafts from the three ceiling openings throw beams of light down the full 120 metres to the floor, which on a clear day produces an effect that photographs have consistently failed to convey.
The name — Majlis Al Jinn, Meeting Place of the Spirits — comes from the local Bedouin communities who knew the surface openings existed and gave them their own significance. Standing at the edge of the main shaft, looking down 120 metres into a chamber larger than ten football fields, understanding why they named it that requires almost no imagination.
Getting There and Getting In
The cave sits on the Selma Plateau in the eastern Hajar Mountains, roughly 150 kilometres from Muscat. The drive involves a 4WD track across the plateau that is, by most accounts, technically demanding. The plateau itself is at around 1,400 metres elevation.
Entry requires abseiling — rappelling — down one of the three vertical shafts. Cheryl’s Drop descends 158 metres. The First Drop is around 120 metres. This is not recreational abseiling. The drops are vertical, the bottom is invisible from the surface, and the return requires ascending the full rope length back out. Currently, visiting Majlis Al Jinn requires a permit from local authorities, appropriate technical caving equipment, and experience in vertical rope work.
The OMRAN Group — Oman’s national tourism development body — has announced plans to develop Majlis Al Jinn as an adventure tourism destination as part of the country’s Vision 2040 framework. When that development is complete, the cave may become accessible to visitors without technical caving experience. As of 2025, it remains a destination for experienced speleologists and guided technical expeditions.
- Source: OMRAN Group developing Majlis Al Jinn as part of Oman Vision 2040 tourism strategy. Source: British Muslim Magazine
- Permit: A permit from local authorities is currently required to visit Majlis Al Jinn. Contact Oman’s Ministry of Heritage and Tourism
Al Hoota Cave — The Accessible One
While Majlis Al Jinn sits at the extreme end of the cave-visiting spectrum, Al Hoota Cave sits at the other. Located near Al Hamra in the Western Hajar, adjacent to Muscat International Airport, Al Hoota is the only developed show cave in Oman — and the first show cave opened on the Arabian Peninsula when it launched in 2006.
The cave is 5 kilometres long, contains four underground lakes, and hosts over 100 animal species, including the Garra Barreimiae — the Omani blind cave fish, a species found nowhere else on Earth. This species has evolved over thousands of years in the cave’s underground lakes, losing its eyesight and pigmentation entirely. The standard guided tour covers 500 metres along a purpose-built walkway, ending at the first underground lake where the fish can sometimes be seen near the surface.
Al Hoota is detailed in its own guide on this site. For caves in the Hajar Mountains that a visitor without technical experience can actually see, it is the starting point. The geological exhibition at the visitor centre explains how the cave formed and provides context for everything else in this guide.
- Hours: Sunday to Thursday: 9am–5pm. Friday: 9am–12pm then 2pm–5pm. Closed Monday.
7th Hole Cave — Adventure Caving in the Hajar
The 7th Hole is one of the Hajar Mountains’ most spectacular cave systems, and one that Guide Compass runs tours into regularly. Unlike Al Hoota’s walkway-and-lighting approach, the 7th Hole requires real participation: crawling, scrambling, squeezing through passages, and navigating cave features that don’t simplify themselves for the visitor.
The cave gets its name from its seventh chamber — a high-ceilinged cavern with formations that the preceding six passages give no indication of. The approach through the earlier chambers is tight in places. Some sections require moving sideways. Headlamps are essential, not a gesture toward atmosphere. The cave environment is cool and damp throughout, and the transition from the mountain heat outside to the cave interior is something you feel immediately.
This is a guided experience — the cave requires knowledge of the route, appropriate lighting, and someone who understands the terrain. Groups are small. The full tour runs approximately three to four hours.
Tahery Cave — The System Beyond
Tahery Cave connects to the 7th Hole system in its deeper sections, and the multi-day expedition that traverses from the 7th Hole through to Tahery is one of the more serious caving adventures available in Oman. Tahery itself features winding passages, underground chambers, and natural formations that have developed in isolation from the surface for a very long time.
Bimmah Sinkhole — Limestone Collapse
Bimmah Sinkhole is not a cave in the technical sense. It is a doline — a collapsed limestone cavity — that has filled with turquoise water and become one of the most visited geological features on the east coast road between Muscat and Sur.
The collapse that created Bimmah happened relatively recently in geological terms, and the resulting hole — roughly 40 metres across and 20 metres deep — connects to the sea through subterranean fissures. The water inside is a mix of fresh groundwater and salt water, which produces the vivid turquoise colour and supports a small population of fish. You can swim in it. Most people do.
It sits directly on the coastal road, has a car park and basic facilities, and takes about thirty minutes to visit properly. As an introduction to what karst processes do to limestone — the same processes responsible for Al Hoota Cave and Majlis Al Jinn, just at a much smaller and more recently revealed scale — it is genuinely worth the stop.
Tawi Ateer — The Sinkhole of the South
In the Dhofar Mountains near Salalah, far from the main Hajar cave systems, Tawi Ateer (Bird’s Well) is a massive sinkhole roughly 200 metres in diameter and over 200 metres deep. It is not a cave in the sense of having accessible passages, but as a karst feature it rivals anything in the north in terms of scale. The sinkhole hosts bird colonies — the name refers to the birds that nest in the cliff walls — and the view down from the rim is substantial enough to produce genuine vertigo.
Tawi Ateer is worth including in any southern Oman itinerary that covers the Dhofar highlands, combined with the Wadi Darbat and Mughsail Beach visits that form the core of a Salalah circuit.
What Lives in the Hajar Mountain Caves
Cave ecosystems are among the most specialised on Earth. The absence of light removes the foundation of most food chains — photosynthesis — and the organisms that survive underground have found alternative strategies over thousands of generations of isolation.
Garra Barreimiae Fish
The Garra Barreimiae in Al Hoota Cave is the most dramatic example in Oman. The blind cave fish has lost its functional eyes — skin has grown over them — and its pigmentation has faded to near-transparency. Its lateral line system, which detects vibrations and water movement, has become more acute to compensate. This is not a recent adaptation. The evolutionary timeline required to produce these changes runs to tens of thousands of years at minimum.
Bats
Beyond the fish, the Hajar cave systems host populations of bats — the most important predators in the cave food chain, and the primary input of nutrients from the surface world into the cave ecosystem through their guano. Cave crickets, spiders, beetles, molluscs, and a range of arthropods occupy the different zones of the caves, each adapted to the specific conditions of their section — the twilight zone near entrances, the dark zone of the deeper passages, and the deep zone where temperature and humidity are most stable.
Majlis Al Jinn’s chamber supports a population of bats whose flight through the sunlight beams from the ceiling openings has been described by the few people who have witnessed it as one of the more extraordinary things they have seen underground.
Planning a Cave Visit in Oman
What’s Accessible Without Technical Experience
Al Hoota Cave is the only developed show cave and requires nothing beyond a ticket and appropriate footwear.The tours at the 7th Hole and Tahery Cave are open to guests who may not have any previous caving experience but are in good shape and comfortable in enclosed spaces. Bimmah Sinkhole requires nothing at all beyond the ability to walk down a path.
Majlis Al Jinn currently requires technical caving skills, proper equipment, a permit, and an experienced guide. It is not accessible to casual visitors in 2025 but is being developed for broader access as part of Oman’s Vision 2040 tourism strategy.
What to Wear and Bring
- When preparing for your adventure, remember to pack your own headlamp and ensure you’re familiar with safety protocols before heading out.
- Knee pads can be beneficial for any crawling sections, although they aren’t a must-have.
- Bring gloves to protect your hands against rough rock surfaces.
- Lastly, opt for long sleeves and trousers for better practicality instead of shorts.
Season
The caves themselves are around 20 degrees Celsius year-round. The access roads and the surface conditions are the variable. October to April is the most comfortable for the drive to cave access points in the Hajar Mountains and for the physical activity of caving. Summer heat outside the cave makes the pre- and post-cave experience more demanding, though the cave interior itself is a relief from it.
FAQs
Majlis Al Jinn (Meeting Place of the Spirits) in the eastern Hajar Mountains is the largest cave chamber in Oman and the second largest known cave chamber in the world by floor area — 58,000 square metres, 310 metres long, 225 metres wide, and 120 metres high. The Great Pyramid of Giza fits inside with room to spare. It is currently accessible only to experienced cavers with technical equipment and a permit.
Currently, Majlis Al Jinn requires technical caving equipment, rope work experience, and a permit from local authorities. It is not open for casual tourism. However, Oman’s OMRAN Group has announced development plans to make it accessible to general visitors as part of Vision 2040 — when that infrastructure is complete, the cave will likely become one of the most visited attractions in Oman.
Al Hoota Cave (near Al Hamra) is the only fully developed show cave in Oman with guided tours, walkways, and visitor facilities. The 7th Hole Cave and Tahery Cave in the Hajar Mountains are accessible on guided adventure caving tours for visitors with no prior technical experience. Bimmah Sinkhole on the east coast is open to all visitors and requires no special equipment.
The limestone in which the Hajar Mountain caves formed dates to the Eocene epoch — 40 to 50 million years ago, when the region was a warm shallow sea. The cave chambers themselves formed more recently through the dissolution of that limestone by acidic groundwater, a process that has been active for several million years during wetter climatic periods. Al Hoota Cave is estimated at 2 to 3 million years old. Majlis Al Jinn’s chamber formed over a similar timescale within older rock.
At the developed and guided level — Al Hoota Cave’s walkway tours, Guide Compass cave tours to the 7th Hole and Tahery — yes. The caves are well-understood, routes are known, and guides carry appropriate equipment. Technical caving in undeveloped cave systems carries real risks that require proper training and equipment. Majlis Al Jinn, in particular, should not be attempted by anyone without vertical rope work experience and appropriate gear.
Al Hoota Cave contains the Garra Barreimiae — the Omani blind cave fish, a species found nowhere else on Earth. Over thousands of years of evolution in the cave’s underground lakes, it has lost its functional eyes (skin has grown over them) and its pigmentation has faded almost to transparency. The cave is also the longest in Oman at 5 kilometres, contains four underground lakes, and was the first show cave opened on the Arabian Peninsula.
Cave Tours with Guide Compass
The 7th Hole and Tahery Cave are part of our adventure tour programme in the Hajar Mountains. If caving is something you want to add to your Oman itinerary, we can connect you with the right specialist operators and build it into a wider trip that covers the mountains, heritage sites, and wadis of the interior.
Message us on WhatsApp with your dates and what you’re looking for — we’ll put together a plan that fits.
