FACTBOX: Pompeii: a sad decline

(Reuters) - The Italian government declared a state of emergency at the Pompeii archaeological site earlier this month to try to rescue one of the world's most important cultural treasures from decades of neglect.

Some 2.5 million tourists visit Pompeii each year, making it one of Italy's most popular attractions, and many have expressed shock at the site's decay.

Here are some key facts about Pompeii:

BACKGROUND:

* Pompeii was buried under a deep layer of ash in an eruption of the Vesuvius volcano, which towers over the Bay of Naples in southern Italy, in AD 79.

* The site is famous for the vignettes of everyday life preserved in the ash -- writhing victims, everyday households and even a brothel with lurid murals.

ERUPTION:

* Pompeii, ancient city in the Campania region of western Italy, was 14 miles southeast of Naples, at the southeastern base of Mount Vesuvius. It was built on a spur formed by a prehistoric lava flow to the north of the mouth of the Sarnus (modern Sarno) River and had a population of 13,000.

* Mount Vesuvius erupted on August 24, 79 AD. A vivid eyewitness report is preserved in two letters written by Pliny the Younger to the historian Tacitus, who had inquired about the death of Pliny the Elder, commander of the Roman fleet at Misenum.

-- Pliny the Elder had rushed from Misenum to help the stricken population and to get a close view of the volcanic phenomena, and he died at Stabiae.

* Just after midday on August 24, fragments of ash, pumice, and other volcanic debris began pouring down on Pompeii, quickly covering the city to a depth of more than 9 feet and causing the roofs of many houses to fall in.

COVERED:

* Additional pyroclastic flows and rains of ash followed, adding at least another 9 feet of debris and preserving in a pall of ash the bodies of the inhabitants who perished while taking shelter in their houses or trying to escape.

-- A pyroclastic flow is a ground-hugging avalanche of hot ash, pumice, rock fragments and volcanic gas, which rushes down the side of a volcano as fast as 100 km/hour or more.

* The city's sudden burial served to protect it for the next 17 centuries from vandalism, looting, and the destructive effects of climate and weather.

EXCAVATIONS:

* The ruins at Pompeii were first discovered late in the 16th century by the architect Domenico Fontana. Herculaneum was discovered in 1709, and systematic excavation began there in 1738. Work did not begin at Pompeii until 1748.

* In 1997 the U.N.'s culture agency UNESCO added Pompeii to its list of sites of "outstanding universal value". The latest state of emergency will last for a year and allows for extra funds and special measures to be taken to protect the site.