After seven hot summers of digging, an Italian archaeological team believe they have discovered one of the most important sites of the ancient world.
Fanum Voltumnae, a shrine, marketplace and Etruscan political centre, was situated in the upper part of the Tiber river valley.
It lies at the foot of a huge outcrop of rock, upon which is perched the mediaeval city of Orvieto.
A walled sanctuary area, 5m-wide (16ft) Etruscan roads, an altar, and the foundations of many Roman buildings that have laid buried for two millennia have been discovered.
And as the dig closed for the 2007 season, with tarpaulins being pulled over ruins to protect them from the winter weather, Professor Simonetta Stopponi of Macerata University was upbeat about the site's significance.
"I am confident that for the first time we have positively identified one of the most important lost sites of the ancient world," she told the BBC.
Fanum was already famous in antiquity as a religious shrine and a meeting place where the 12 members of the Etruscan League, a confederation of central Italian cities, used to gather every spring to elect their leader.
In the autumn of 398BC an extraordinary policy meeting was held in Fanum.
A Roman army had been besieging the town of Veii, a wealthy member of the Etruscan League, which lay only 16km (10 miles) north of Rome.
The citizens of Veii, exhausted by years of warfare, appealed for help and asked the other members of the league to join them in declaring war on Rome.
The gods of the shrine of Fanum were duly consulted, but the vote went against collectively defending Veii.
Two years later the town fell to Rome.
Beginning of the end
It was the beginning of the end for the Etruscan League, all of whose cities eventually fell to Roman invaders.
We know all this ancient history through the Roman historian Livy, who wrote his famous account of the origins of Rome towards the end of the 1st Century BC.
Livy mentions Fanum, and stresses its importance no less than five times.
But he failed to mention where Fanum was situated, and after the fall of Rome, all memory of its exact location was lost.
The sacred zone is being systematically dug up by an enthusiastic team of young archaeologists wielding picks, shovels and trowels.
They come from America, Mexico and Spain as well as from Italy.
For 2,000 years, from the 5th Century BC until the 15th Century AD, large numbers of people used to gather at Fanum every spring.
In Etruscan times it was a place for the political leaders of central Italy to take stock of military and civil affairs, and to pray to their gods.
Later, under the Romans, according to researchers, Fanum continued as the site of an important annual spring fair.
Athletes took part in public games, and priests and politicians mingled with crowds of ordinary people who came to buy and sell livestock and agricultural products.
As recently as the 19th Century there was a cattle market held here. The area is still known locally as Campo della Fiera, or Fair Field.
A first Christian church was built on the site as early as the 4th Century. You can see part of its patterned stonework floor.
The foundations of a later 12th Century church dedicated to Saint Peter have also been laid bare.
Following the Black Death, the 14th Century plague, and perhaps because of it, the church was abandoned and left to ruins.
Funds for the dig have come in part from an Italian bank, the Monte Dei Paschi of Siena, in part from the EU, and in part from the local regional government.
Absolute certainty that this was the site of Fanum can only come with the discovery of written inscriptions dedicated to the Etruscan god Voltumna, the most important deity worshipped by the inhabitants of this part of Italy.
So far only votive objects such as small bronze statues, or pieces of painted terracotta roof tiles from the temples have been dug up, nothing written.
But Professor Stoppani says she is 99% sure that the site has yet to give up the last remains of ancient Fanum.
She plans to continue the dig next year.