The mastodons roamed along the banks of a river, munching on the vegetation under the canopy of a tropical forest, oblivious to the screams of  monkeys and the presence of rhinos, but watching out for lions and sabre-toothed tigers that were never far from the watering hole.

The river attracted all of these animals but, from time to time, a visit here could prove fatal. As the water swept away the remains of the dead bodies, they eventually started to pile up at one of the bends of the river. There the bones accumulated, along with other debris, and over time they fossilised.

This was how the Pliocene paleontological site at Dorkovo village, near Velingrad in the Rhodope, was formed.

This is what the surroundings of Dorkovo looked like in the Pliocene, according to the museum’s diorama

Bulgaria's historical heritage is so rich that its paleontological sites are overlooked. Dorkovo is one of the most significant of them. It belongs to the Pliocene era, the time between 5.3 million and 2.58 million years ago when the modern continents were almost formed: the Mediterranean Sea was being created from what remained of the ancient ocean Tethys, the land connections between North and South America and between Asia and Alaska were established, the overall climate was hotter and the sea level was 25 metres higher than it is today. The Pliocene was also the time when, in faraway Africa, the first apes and our distant ancestor, the Australopithecus, appeared.

The remains of the prehistoric animals near Dorkovo were first discovered by a local teacher in the 1930s, but it was not until the early 1980s that geologists revisited them, triggering the interest of palaeontologists. In 1985-1987, a Bulgarian-French expedition surveyed the site only to realise that they had stumbled upon one of the richest finds of early Pliocene fauna in Europe and the richest one of Anancus arvernensis mastodons on the continent, including calves still with their baby teeth. About 3 metres tall and weighting up to 5 tons, these giants looked like modern elephants, but had much longer tusks reaching up to 3m in length. While mastodons are relatives of the more famous woolly mammoths, they are a different genus and became extinct much earlier, at the beginning of the following geological epoch, the Pleistocene.

Paleontologists have discovered near Dorkovo the largest deposit in the world of bones from over 30 species in a single location. On an area of just 15 sq m, more than 600 bones have been found. The deposit has not been fully excavated, and some bones are still visible, protruding from the rocks

The idea for the creation of a museum on the site at Dorkovo appeared for the first time in 1987, but actual work started in 2008. Construction began in 2012, as part of a project to promote the village as a tourist destination. In 2013, the Pliocene museum was opened: a novelty for Bulgaria as it combined modern architecture and interactive displays.

The small museum is dominated by a model of a mastodon, an exhibit of real tusks (found not here, but around Yambol about 200 kilometres away) and of some fossils, a recreation of a paleontological excavation site and a 10-metre diorama recreating the habitat of these prehistoric animals. There is also a proper soundscape.

When the museum opened, in 2013, its modern architecture and immersive atmosphere were a novelty for Bulgaria

The ticket also covers the entry fee to the nearby mediaeval fortress Tsepina. Both sites are an easy trip by car from Velingrad.

For more of Bulgaria's paleontological past, including the sight of the strange Deinotherium, which was related to elephants, and had backward facing tusks in its lower jaw, visit the Paleontological Museum at Asenovgrad (Badelema neighbourhood, 212th St), and the Museum of Palaeontology and Historical Geology at Sofia University (main building, north wing, floor 5).