TEHRAN -- Beneath the rugged mountains of western Iran, the caves of Ilam Province preserve an unusual record of both natural history and human occupation. 
Some shelter thousands of bats and other animals; others contain evidence of human presence dating back to the Paleolithic period, while their chambers preserve striking geological formations that remain only partly studied.
Ilam’s mountainous landscape, bounded by ranges including Kabir Kuh, Dinar Kuh, Siah Kuh, Laneh, Gachan, Charmin, Shalam, Bankul, Sharehzul, Sivan, Manesht and Qalarang, is particularly rich in caves and smaller rock shelters. Many remain unexplored, according to provincial specialists, leaving their geological, biological and archaeological potential largely undocumented.
Most natural caves form through the dissolution of limestone as water penetrates the rock, although geological faults, folding, wind erosion and rockfalls can also contribute to their formation. Over time, these processes create underground chambers decorated with stalactites, stalagmites, columns and other mineral formations.
In Ilam, the geological diversity is reflected in the caves themselves. According to Haji Karimi, a geology professor and faculty member at Ilam University, most of the province’s caves are limestone formations, with those associated with the Asmari and Sarvak formations representing two major geological groups. Caves in the Kabir Kuh range are associated with the Sarvak Formation, while 
caves around Ilam are largely associated with the Asmari Formation.
Some caves may be tens of millions of years old. Karimi estimated the age of caves such as Kenna Agha Cave, also known as Agha Mir Cave in Malekshahi County, at more than 70 million years, although the source notes that systematic research into the age and palaeoenvironment of Ilam’s caves remains limited.
Not all of the caves are equally stable. Huvir Water Cave in Dehloran and Mojareh Cave in Abdanan are gypsum caves, whose geological structure makes them less stable than limestone systems. Karimi cautioned that visitors should not enter such caves without appropriate equipment and experienced guides.
The province’s caves are also important biological refuges. Dehloran’s Bat Cave is the best-known example, supporting thousands of bats and a variety of other cave-dwelling organisms. Tourism sources describe the cave as lying near Dehloran’s hot springs on the slopes of Siah Kuh and as a notable habitat for bats.
According to Alireza Mohammadi, deputy head of natural environment and biodiversity at the Ilam Department of Environment, 34 caves have so far been identified within environmentally managed areas of the province. Given Ilam’s extensive mountainous terrain, he said, additional caves are likely to remain undiscovered.
The conservation status of several caves reflects their biological importance. Muhammadi said Bat Cave and Huvir Cave have been placed in the highest category of conservation importance, while Kolah Piekeh, Telem and Chehel Sotoun caves have been assigned the second category.
The archaeological record adds another layer to Ilam’s subterranean landscape. Thirty caves outside protected environmental areas have been nationally registered, according to Jamal Sheikhi, an archaeologist and researcher with the provincial cultural heritage authorities. Twenty-six are registered as historical sites or human settlements and four as natural heritage sites.
Archaeological investigations at caves including the Zanjireh Twin Caves, Shabab Cave and Rock Shelter, Gorgehlan, Sabz Ali and Darreh Zamin have produced evidence of human occupation dating from the Paleolithic, in some cases to around 150,000 years ago, through later periods. Some sites also contain evidence extending into the Sasanian era.
Yet much remains to be documented. Sheikhi said another 20 caves have been identified but have not yet undergone full documentation. Once surveyed, those meeting the necessary criteria can be proposed to the Ministry of Cultural Heritage, Tourism and Handicrafts for registration.
That unfinished inventory also points to the province’s tourism potential. Most caves lie in remote mountain areas without public access or adequate infrastructure, meaning organized cave tourism has yet to develop. Darreh Zamin Cave in Zanjireh, however, already has an access route and, with its springs, cliffs, archaeological cave and largely untouched landscape, could become a destination for adventure and nature tourism.
The challenge is to develop that potential without destroying what makes the caves valuable. At Barreh Zard Cave, for example, careless visitors have damaged stalactites and crystalline formations. For Ilam, the caves represent a rare convergence of geology, biodiversity and human history—and a largely unfinished scientific record beneath the mountains.