The “Pyramids” are located in the hills near the town of Visoko, northwest of Sarajevo.
The fortress was built over an old Roman Empire observation post, which in turn was constructed over the ruins of an ancient settlement.
The hills themselves, which form striking pyramidal shapes, are a type known as flatirons. Archaeological geologist Paul Heinrich of Louisiana State University has pointed out that these formations are common throughout the world, giving the example of the so-called ‘Russian Twin Pyramids’ in Vladivostok.
Tunnels around the hill complex, which have been named Ravne tunnels, are claimed to be an ancient man-made underground network.