The trouble with digging up the ancient past is that only the best and the biggest stuff tends to get left behind. Not so in Pompeii. In this brilliant portrait of the “life of a Roman town”, Mary Beard uses the relics buried by the eruption of AD79 (the fish-weighing scales and flour mills, the gladiators' helmets and grafitti) to bring everyday Roman culture alive.

Beard covers the big public issues - economy and government, gods, games - and animates them superbly by tying them to the biographies of real Pompeiians: the heart-throb gladiator Celadus, the well-connected local worthy Marcus Holconius Priscus, and the warty banker Lucius Caecilius Jucundus. She is most interested, however, in the domestic and the intimate. In the excellent chapter on painting and decorating, she doesn't just analyse Pompeiian style, she opens up cupboards to count the paint pots and turn over the spoons and spatulas. She doesn't only describe the grander rooms with their fantastical frescoes and deep tones of “Pompeiian red”, she explores the corridors and service quarters, revealing the ferocious zebra-stripe colour scheme “which would not have looked wholly out of place in the 1960s”.

Pompeii's smells must have been no less vibrant than its colours. The 20,000-seater amphitheatre had no lavatory. Huge local fortunes were built on a kind of fermented (rotted, some say) fish sauce. As for the Roman baths, they were apparently “a seething mass of bacteria”, which weren't regarded as safe to enter with an open wound. Cleanliness aside, they sound closer in spirit to a 1970s San Francisco bathhouse than, say, today's sleek spas.

Rome's famed hygienic fastidiousness is not the only classical myth that Beard delights in busting. Togas, when they were worn at all, came in fierce colours, not just white. Losing gladiators were much more likely to survive than be killed. And if the cramped dining rooms and minuscule kitchens of Pompeii are any guide, the decadent banquet of the celluloid imagination was probably a rare affair. The notorious dormice dipped in honey really were a Pompeiian treat - the jars found with internal, premoulded dormouse exercise runs prove it - but the wealthy largely made do with a “finger buffet” of bread, olives and cheese, perhaps with sausages and black pudding. The poor, it seems, dined out at simple cafes.

Times Archive, 1829: Excavations at Herculaneum And Pompeii

There are grotesque designs, such as a pigmy teaching an ape to dance, as well as paintings of fruit and animals beautifully executed

• The excavations now in progress at Herculaneum and Pompeii

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• The love lives of the ancient Romans

Most shockingly, the Romans were not quite as morbidly hypersexual as we like to imagine. The Stabian Baths were indeed brightened up by athletic-erotic scenes - including depictions of both a trio and a foursome. Carved phalluses and boastfully obscene graffiti really are found everywhere. But much of what has been called erotic, Beard protests, is more “a familiar and slightly edgy mixture of sex, drink and play” than evidence of “terrible moral turpitude”.

Beard is interested in Roman sex. She spends a good deal of time untangling what she wryly calls the “Pompeiian Brothel Problem” - the problem being how many there actually were. Some archeologists see brothels wherever a phallus is carved or painted, an erotic painting displayed, or a randy graffito scrawled. Some reckon that, on this basis, there were 35 brothels in the city, or one for every 75 free adult males. More cautious scholars insist that the only sure test for a brothel is for a building to have a masonry bed near the street, explicitly sexual paintings and graffiti clusters “of the ‘I f***ed here' type”. By that test, the city chalks up one solitary brothel. The brothel gap - 35 or just one? - is a classic example of the quarrels that enliven Pompeiian archeology. The city is exciting partly because it's a vast forensic puzzle. Beard is a classicist, however, not an archeologist, and rather than advancing eye-catching new theories she prefers judicious evaluation. Her sensible answer to the brothel conundrum is to warn that searching for physical evidence of commercial sex is a category mistake. Would we know a brothel today by its layout, or by its contents?

This is a meticulous, vivid study of Pompeiian life, and it rightly and resolutely focuses on the living city. Occasionally, we get alluring glimpses of the book that Beard might have written: on the discovery of Pompeii and its cultural afterlife. We learn that Mozart visited in 1769, picking up ideas for The Magic Flute. We discover that Edward Bulwer-Lytton's romance, The Last Days of Pompeii (1834), was one of the bestselling novels of the 19th century, and that Second Empire aristocrats in Paris played at Romans in what must have been the original “toga party”.

“Pompeii” the archeological miracle has surely had as great an impact on the world as Pompeii the provincial Roman city, and these asides leave us wanting more. This is no more a tourist guidebook than it is a cultural study, but Beard does throw in a few practical tips at the end. “Go in to any house you find open,” she advises.

This isn't as obvious as it sounds. Today, only a third of the site is officially accessible - and that is when there isn't a wildcat strike in action. Travellers tell tales of endless barriers and signs protesting that an area is in restauro - without any apparent signs of work going on.

Beard doesn't discuss why it is so difficult to see much of the site, other than to observe that the administration is underfunded, but there's surely more to it than this. In July 2008, the Italian government declared a Pompeiian “state of emergency”, citing the terrible damage being done by erosion, theft, vandalism - and, of course, mass tourism.

Beard claims that a visit “almost never disappoints”, but the gulf between the vibrant city she evokes and the decaying, barred-off ruin described in the newspapers suggests that, after reading this wonderful book, a trip to the Bay of Naples may be too painful to bear.

Pompeii by Mary Beard
Profile £25 pp360

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