Thanks to political tensions easing in Lebanon, archaeologists have finally managed to locate the sites of ancient Phoenician harbours in the seaports that dominated Mediterranean trade thousands of years ago.

By drilling out cores of sediment from the modern urban centres of these cities, geologists have mapped out the former coastlines that the sediments have long since buried. From this they have pinpointed the likely sites of the old harbours, and have marked out locations that, they say, are in dire need of exploration and conservation.

The modern cities of Tyre and Sidon on the Lebanese coast were once the major launching points of the seafaring Phoenicians. They were to the ancient world what Venice, Shanghai, Liverpool and New York have been in later times: some of the greatest of the world's ports, and crucial conduits for trade and cultural exchange. From the harbours of the Phoenician cities, ships carried precious dyes and textiles, soda and glass throughout the Mediterranean and beyond.

Both cities still carry the same name, but the coastlines on which they sit have been reshaped by silting since the time of the Phoenicians, about 3,000 years ago. Sidon has extended out to sea through the build-up of silt. And Tyre, which was once an island, has been joined up to the mainland by silting, while much of the old land has sunk beneath the waves.

But whereas these major geographical changes were roughly known, no one knew the exact shape of the old coastline, which would in turn reveal the positions of the ancient harbours themselves.