Where was the capital of Tartessos, the legendary pre-Roman civilization which once existed on the Iberian Peninsula?

The culture which flourished from around 800 to 500 BC is believed to have been located mainly around the present-day cities of Cadiz, Seville and Huelva in southern Spain, but no traces of a major urban settlement have been found.

Now, however, scientists have discovered surprising clues to where a major Tartessian city may have been, the daily El Pais reported.

Its ruins could lie in the subsoil of a marsh area known as the Marisma de Hinojos in the Donana National Park near Seville, according to the daily.

Chief researcher Sebastian Celestino declined to comment on the report. His team will give details once the investigation is finished, a representative of the Superior Council of Scientific Investigations (CSIC) told the Deutsche Presse-Agentur dpa.

For years, satellite and aerial images of the Marisma de Hinojos have revealed strange circular structures of different sizes - up to 200 metres in diameter - and rectangular forms.

The area is under water in wintertime, and until now, scientists had thought it had always been inundated.

That had made most of them skeptical of the possibility that the forms visible from the air could be remains of a human settlement buried in the subsoil.

Yet new evidence has now emerged, with electro-magnetic tests indicating that the area may have experienced long dry periods, according to El Pais.

In the bottom of the marsh, there are layers that appear to contain concentrated sand, the daily quoted researcher Antonio Rodriguez as saying.

If the area had always been submerged, the subsoil would only contain mud instead of sand.

Scientists think they stand a fair chance of finding archaeological remains in the marsh, though the link with Tartessos remains a mere hypothesis for the time being.

Knowledge about Tartessos had so far been based mainly on Greek and Latin literary sources, which described it as a civilization on the edge of the known world.

Often identified with Tarshish mentioned in the Bible, the kingdom traded profitably with the Phoenicians and Carthaginians, and may even have discovered a route to Britain.

Some researchers equate Tartessos with Atlantis, the utopia described by the Greek philosopher Plato, which is said to have sunk into the sea.

Tartessos disappeared mysteriously around 500 BC. Some believe it was destroyed by the Carthaginians, but the new geological evidence from the Marisma de Hinojos makes it look possible that two tsunamis wiped out the settlement located there, according to El Pais.

Some remains identified with Tartessos have been found, including a palace-sanctuary near Badajoz and a necropolis in Huelva, but no major urban settlement.

As the next step, scientists intend to make a hole 7 metres deep into the marshland to see what - if anything - lies underneath.

If the remains of a Tartessian city were found, that might bring invaluable information to historians divided over whether Tartessos had an identity of its own, or whether it was just an extension of the Phoenician civilization.