It is impossible not to stare. The Roman man in front of us was overwhelmed by a surge of volcanic gas while he went to bathe in Pompeii one afternoon in 79AD, but his facial features look almost as clear now as they might have been then.
He could be the man standing next to me. Little wonder, then, that both of us are pacing around the glass case and peering in at the cast that preserves his remains so perfectly you can still see the imprint of his toga.
Around us, people are jostling for position. The British Museum's blockbuster exhibition on Pompeii, which continues in London until September, has increased visitor numbers to this already crowded tourist destination, and it shows.
A visiting priest calls for hush. There are, after all, two deceased human souls in the room. The other man is a slave – you can tell by the big belt he is clearly wearing around his waist, the guide explains. There is quiet for a moment before the cameras start flashing again.
But that's just it: Pompeii, the ancient city buried for centuries after Vesuvius's most terrifying eruption nearly 2,000 years ago, is so much more vivid than any book can convey that you want to capture it on film before the old volcano blows her top again.
And another big eruption is due, putting the lives of the quarter of a million Italians who live in the 'red zone' at risk. The volcano has been silent since 1944, but experts are predicting the same kind of catastrophic eruption that destroyed Pompeii and its neighbouring town Herculaneum all those years ago.
On that fateful day on August 24, "a black and dreadful cloud" burst out of the volcano and "yawned open to reveal long fantastic flames, resembling flashes of lightning but much larger", wrote eye-witness Pliny the Younger, who watched in horror across the Bay of Naples.
A dreadful darkness descended on Pompeii, and buildings seemed "to rock to and fro as if torn from [their] foundations", he wrote. Terrified inhabitants tied pillows to their heads with napkins as they fled the torrents of ash and pumice stones raining down upon them.
Contrary to popular belief, many managed to leave the town. What we see today is not the Marie Celeste ghost town that has gained mythical status in the public imagination, but a city already in full flight.
Archaeologists estimate that 2,000 people died, a tenth of the 12,000-strong population. How far those who fled got is uncertain, but most of those left behind were killed by a violent surge of burning gases unleashed some 12 hours after the initial eruption.
Before the city was buried, say the experts, you have to imagine a mass exodus: people grabbed what they could and fled with donkeys, carts and barrows clattering along the deep grooves that are still visible on the town's labyrinth of paved streets. You can still see the holes on the pavements that were once used to tie up those donkeys and, on one street, a guide says that the quartz stones dotting the road were used as cat's eyes.
There is a crowd of tourists gathered around, contemplating this. It's a Monday morning in mid-summer and, perhaps much like a busy day back in 79AD, Pompeii is bustling.
The forum is packed to capacity and tour groups are fanning out to see the market place, the baths, the basilica, the mosaics, myriad statues and the paintings that, in their heyday, would have turned the town into a "gaudy razzmatazz", as classicist Mary Beard put it, of deep crimson, yellow and blue.
It is a place of exceptional geographical and architectural beauty. The remains of the buildings with their columns, colonnades and statues are exquisite. The paintings and mosaics that once decorated them are stunning.
Too often, the more brash among them – such as the sexually explicit wall paintings that purport to provide a 'menu' of sexual positions in the brothel – grab the headlines, but the mosaic of a dog and the caption 'Cave Canen' (beware of the dog) in the House of the Tragic Poet are just a few of several treasures on view.
Having said that, the brothel is still a big draw. There are queues outside. A guide explains that the price of a prostitute was the same as the price of a glass of wine – and not the best quality wine at that.
But that is not nearly as depressing as feeling like a ghoulish peeping Tom as you file through the brothel's cramped rooms. It's a feeling that returns again and again because the human tragedy of Pompeii is palpable in every corner of this vast town.
In one sumptuously decorated house – the House of the Menander, named after the portrait of the poet Menander on its walls – a glass case holds the skeletal remains of a family huddling together for safety in a room. They believed that the roof would provide protection, but it collapsed, killing them.
Archaeologists later found an exquisite silver tea service wrapped and packed in the basement for safe-keeping. It is now on display at the Archaeological Museum in Naples. They also found the remains of two adults and a child who, some time after the eruption, had burrowed a tunnel into the compounded ash with pick and hoe looking for forgotten booty, but they too were crushed when their makeshift tunnel collapsed on them.
People remembered the volcano and the towns it buried for several decades after it happened. There is evidence that people tried to dig out their belongings and that treasure-hunters attempted to mine for valuables.
But then it was forgotten, and it would be several hundred years before Pompeii was rediscovered in the 18th century. Since then, the town has given up many, but by no means all, of its secrets – a fifth of the town is still under ash.
And yet the picture that has emerged is fascinating. Excavators found the remains of a woman and the baby she was just about to deliver. They uncovered adults in basements, families in flight, a group of youths sheltering in the latrine of the gymnasium, dogs still tied to their posts and, more disturbingly, a slave bound by a leg iron.
As recently as 1981, in nearby Herculaneum, one little boy was found holding his wooden piggy bank; it still had a coin inside. Hundreds more had grabbed their valuables – little statuettes of gods, jewellery and money – and had rushed to the wharf hoping in vain to escape by boat.
What is exceptional about Pompeii, though, are the human casts of the victims, which are on display in glass cases or behind metal grids at various points around the site. They were made in the 19th century when archaeologists filled the cavities left by their decaying bodies with plaster of Paris.
Detailed analysis of the bones still preserved within the casts tells the story of these people's childhood diseases, their arthritis and their tooth decay. The Romans may have developed a concoction to whiten teeth – burnt antler horn mixed with resin and rock salt – but dental hygiene in Pompeii was very poor.
Other details of the daily lives of the people of southern Italy in the first century are fleshed out in remarkable detail. One of the bakeries, complete with kilns and grinding stones, has an oven that looks just like one you might find in a modern pizzeria.
In Herculaneum, Vesuvius dumped several hundred metres of volcanic mud on the town preserving a breathtaking slice of life: a loaf of bread was found in an oven; the brass leg of a bed is still visible in one house; a sliding wooden door can be seen in another and a wooden clothes press in a laundrette.
You don't really need a guided tour to bring either site to life, but an audio guide is indispensable. Pompeii is something of a warren without guidance and the ruins make much more sense with an explanatory word.
Be prepared for the crowds, too. Visiting some of the better-known landmarks can be like hunting for a bargain in the January sales. At one point, we were trapped in the Stabian Baths when a group of some 50 Russians piled in on top of us.
Plan your route before you go and be patient when you get there. When the crowds get overwhelming, head off to a quiet corner of Pompeii and take in the singular nature of this haunted place.