“Pompeii is one of the most significant proofs of Roman civilization and, like an open book, provides outstanding information on the art, customs, trades and everyday life of the past.
The city has re-emerged from the darkness of centuries precisely as it would have been when it was unexpectedly buried in the thick layer of ash and lava which poured down from the devastating eruption of Vesuvius. It was the year 79 A.D. The scale of the tragedy was appalling: in what had been one of the most active and splendid Roman centres, life came to a permanent standstill.
The thick layer of volcanic material which submerged it, made up to a large extent of ash and lapilli – non-hard material, unlike that which covered Herculaneum and which solidified into extremely hard stone -has meant that the city has remained intact until the present day, not only as far as its buildings are concerned, but also as regards the contents inside the houses and shops, providing an absolutely fascinating picture of ‘daily’ life” .
One would certainly not expect a snail sculpture there, but Clemens Brandstetter supplied me the picture below. He found it in the vicinity of the Temple of Apollo, also known as the Temple of Jupiter, in the Forum area of the city .
The following photo  clearly shows a snail in the ornamentation of what seems to be the upper part of a column. Given the context, it may be assumed that this ornamentation at least dates back to the 1st century A.D., and perhaps even earlier.
Remarkably, the snail is shown with all four tentacles; the dextral shell has possibly been modelled after a Helix-like species.
 http://en.wikipedia.org/wiki/Temple_of_Apollo_(Pompeii); http://en.wikipedia.org/wiki/Temple_of_Jupiter_(Pompeii).
 Many thanks to Clemens M. Brandstetter (Buers, Austria) for supplying this picture and data about its location.