The construction is distinctive. Terraces and platforms rise in tiers from the mountain slopes, built entirely from local granite using dry-stone techniques found nowhere else in the region. There are no shaped blocks. Archaeologists studying the walls discovered that builders selected stones found lying around the landscape and fitted them together with remarkable precision, using smaller stones as wedges to prop up and stabilize the structures. Stairs thread between levels. Silos dot the platforms. The two largest sites, DGB-1 and DGB-2, sit only 100 meters apart and are sometimes treated as a single complex. The craftsmanship is patient and deliberate, the work of people who intended to stay.

What makes these sites extraordinary is not just their construction but their age. The plains below the Mandara Mountains have yielded archaeological evidence going back roughly 2,500 years, but the mountains themselves have been largely silent - almost no sites older than 200 years appear anywhere in the range. The DGB complexes are the sole exception, the only coherent habitation sites found in the Mandaras dating back as far as the 15th century. Why these mountains were seemingly empty for so long, and what drew people to build in them when they did, are questions that drive ongoing research. True archaeological excavation only began in 2001, when Nicholas David opened DGB-2 and DGB-8.

The Mafa people still inhabit the region around the DGB sites, and their living traditions offer clues about what these places meant. The sites appeared during a period of severe drought, and based on both the archaeology and contemporary Mafa ritual practices, experts believe the complexes were built as ceremonial structures related to rain and water. At DGB-2 and DGB-8, archaeologists found large quantities of sand and gravel transported from a local river - possibly a physical representation of flowing water brought to the mountaintop as an offering or invocation. The towers and walls have also supported interpretations of the sites as defensive structures, but the ritual hypothesis carries particular weight given the drought conditions under which they were built.

Not everything found at the DGB sites originated locally. Artifacts from outside the region surfaced during excavation, particularly at DGB-1, leading archaeologists including Nicholas David to propose that at least the DGB-1/2 complex served as a place of exchange with peoples to the north. The timing is suggestive. European and Arabic writers from roughly the same period noted the rise of the Wandala, the Mandara Kingdom that grew to dominate the plains below the mountains. Several researchers believe trade occurred between the mountain-dwelling Mafa and the expanding Wandala polity, and that the creation of the DGB sites may be connected to Wandala's emergence. Whether the relationship was cooperative or defensive remains an open question - one that the stones, for now, do not answer.

The DGB sites were inscribed on UNESCO's World Heritage List in July 2025 as the Diy-Gid-Biy Cultural Landscape of the Mandara Mountains, the first cultural World Heritage site from Cameroon -- recognition of their uniqueness within the archaeological record of Central Africa. They overlook the several-kilometer-long Shikewe watershed, a landscape that has changed little since the builders chose these slopes. The mountains remain remote, the excavation work still young. Much of what the DGB sites can teach depends on future seasons of careful digging in a place where the stones were never shaped but were always, it seems, chosen with great care.