Real-life vampires, giant rock vaginas, ancient sites to rival those of Greece and Rome – Bulgaria’s archaeologists are putting their country on the map of world history, but first they have to stop the mafia stealing its treasures.

The illegal diggers come at night with shovels and sacks, hunting through the places where they know the professionals have been. They’re looking for the tonnes of ancient artefacts that lie hidden in Bulgaria’s soil.

In the past two decades, Bulgarian law enforcement agencies say this plunder has turned into a €30m-a-year industry for local gangs, putting it a close third behind drugs and prostitution. The artefacts – gold Roman coins, ancient Greek silver, Thracian military helmets – wind up with falsified documents in auction houses in Europe and North America, or increasingly with wealthy Arab and Asian collectors.

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“You cannot put a value on what is lost because the real loss is information,” says Professor Bozhidar Dimitrov, director of the National Museum of History in Sofia, who has spearheaded efforts to reclaim lost relics. “Even if we recover them, we don’t know where they were originally found, so our understanding of the history is gone.”

Police say there are 300 criminal treasure-hunting gangs in Bulgaria at present, but as many as 50,000 people are thought to be involved in illegal digging in some form. Entire villages have been known to take part in some impoverished corners of Bulgaria.

Belatedly waking up to the scale of the problem, Bulgarian authorities are trying to claw back some of their lost history from around the world.

“The record so far belongs to the Canadians,” said Prof Dimitrov. “A couple of years back, they returned 21,000 artefacts in one go.

“The Italians had so much to return that the minister of culture became worried about the cost of the shipment, so he ordered his entire delegation to carry two extra bags of luggage when they came here. He himself showed up at my office with two huge suitcases full of priceless artefacts.”

Prof Dimitrov’s huge office looks more like a Bond villain’s than that of a historian: wood-panelled walls and a long window staring up at the Vitosha mountains. “It was designed to intimidate guests”, he says between chain-smoked cigarettes – the museum was formerly the residence of Communist dictator Todor Zhivkov, who ruled Bulgaria for 35 years up to 1989.

The Communist legacy is part of the reason why only a quarter of Bulgaria’s treasures are thought to have been discovered so far. Trapped behind the Iron Curtain for half a century, Bulgaria had few tourists, which meant minimal investment in archaeology and preservation.

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This was followed by a decade of political confusion and economic crisis after the fall of Communism, when organised crime groups had almost completely free rein.

“In the Nineties, the police could stop only about 10 per cent of the stuff leaving the country,” estimates Prof Dimitrov. “Things have improved a lot. Now they get about 70 to 80 per cent. The police show up all the time with new hordes they have seized from shops in Sofia.”

As if to prove the point, the professor cuts the meeting short to receive the deputy director of the police, who says he has 2,000 artefacts to hand over, discovered in the basement of a local antiques store.

Historical discoveries have been one of the few bright spots for Bulgaria’s beleaguered economy in recent years, helping to convince the authorities of the need to protect their heritage.

Archaeologist Nikolay Ovcharov – nicknamed “Bulgaria’s Indiana Jones” – has just started the final excavations at Perperikon, a 7,000-year-old sacred site deep in the Rhodope mountains whose highlight is a walk-in vagina.

First discovered in the 1980s when ethnographers interviewed local villagers, Perperikon was in ancient times as famous as the oracle at Delphi in Greece, a place of wild bacchanalian rituals to the goddess Dionysus, and, according to legend, the birthplace of the Greek prophet Orpheus, which counted Alexander the Great among its visitors.

“It rivals Machu Picchu,” says Prof Ovcharov. “Bulgarian archaeology has enormous potential. It can change the way people think about this country. It can give us national pride as well as bringing in a lot of wealth.”

One of the most extraordinary aspects of Perperikon is a nearby fertility shrine – a 10-metre vulva carved in the rock, leading into a womb-like cave. Around midday at the right time of year, a phallus-shaped ray of sunlight reaches an altar deep in the cave.

“It felt very unusual standing in a vagina,” says Prof Ovcharov, remembering the moment he first saw the cave in 2002. “It was so unique. It still makes my hair stand on end.”

The big surprise for Bulgaria’s historians has been the global interest in its vampires.

A grave unearthed in the Black Sea resort of Sozopol last year turned up a skeleton with an iron stake through its rib cage. It belonged to a famous 14th-century pirate named Kirov, whose job was to attack the ships of illegal Venetian traders. He was later made governor of the town.

Locals believed the souls of evil men did not ascend to heaven and instead left their graves at night to drink the blood of the living. Although Kirov was given an aristocrat’s burial, locals evidently thought him a nasty piece of work, and snuck in after the funeral to drive a stake through the body in order to keep his soul from escaping. They pulled out his teeth, too, just to be safe.

The discovery reached the press almost by accident. Prof Dimitrov was sneaking a cigarette outside Sozopol’s town hall just after the grave was found and some journalists came up to tease him about his heavy smoking. He only mentioned the vampire to deflect attention.

“Suddenly, it became a huge international sensation,” he says at his office, lighting another cigarette. “Vampires are very common here – we’ve already found more than a hundred – so we hadn’t thought to publicise it. I didn’t know there was a vampire movie with Brad Pitt and that they were so popular. It was featured in over 1,200 publications. That’s more than covered the fall of our Communist dictator.”

The vampire has proved a great pull for tourists, and drawn further attention to the astounding discoveries being made in Sozopol.

In 2010, a marble box containing a tooth and bits of skull were found on an adjacent island which are said to be relics of St John the Baptist. Foreign experts dated them to the first century AD and said the DNA belonged to a Middle Eastern man, making the claims plausible enough to attract coach-loads of pilgrims.

Another site in the town has uncovered the ruins of Roman baths alongside a Greek temple to the God Poseidon and a medieval church – a rare chance to see the evolution of worship in a single spot.

This is not so surprising for Bulgaria, a country whose strategic location at the crossroads of Europe and Asia has made it one of the world’s most sought-after territories throughout the ages. Greeks, Romans, Thracians, Byzantines and Ottomans all fought countless wars to gain control of its fertile lands – a bitter irony given the controversial emigration of young Bulgarians over the past two decades.

Not all are happy with the government’s efforts to control the trade in historical artefacts, however. Bulgaria’s small shopkeepers complain about restrictions on selling any pre-twentieth century objects.

“The police can shut me down for having just one old coin,” says Constantine Georgiev, owner of a small bric-a-brac store in Sofia. “But this just means the trade in antiques is controlled by around 10 very rich guys with political connections. No one goes after the big mafia bosses because they can afford the bribes.”

Efforts to increase sentences for illicit smugglers have started to change attitudes towards a crime that was not taken too seriously in the past.

“Many used to see it as a fun adventure,” says Prof Dimitrov. “The men dig while the women do a barbecue. You had police and even priests taking part.”

Indeed, a 41-year-old priest from the northern city of Vratsa was busted in 2010 after conducting over 1,000 illegal sales of ancient coins and jewellery over the internet.

But despite these efforts, experts say that widespread corruption and the high demand from overseas means Bulgaria’s treasures will continue to disappear into private collections, while authorities face a relentless challenge trying to protect over 40,000 known archaeological sites across the country.

“We lobbied for an amnesty a few years back so that private owners could declare what they had on the condition it was not sold or exported. That was one of the first laws that was overturned when GERB [a right-wing Bulgarian political party] took power in 2009,” says Prof Ovcharov. “Rich collectors are a powerful lobby.”