They believe that Tartessos, a wealthy civilization in southern Iberia that predates the Phoenicians, may have had its capital in the heart of what is now the Donana national park.
Until now historians had dismissed the region as a possible site believing that it had been submerged since the ice age. But it is claimed new evidence suggests the waters may have receded in time for the Tartessians to build an urban centre, which was later destroyed in a tsunami.
The Hinojos marshes, an area close to the mouth of the Guadalquiver river where it meets the Atlantic, have now been pinpointed as the site most likely to provide evidence of a lost city.
Archaeological findings have already proved the existence of Tartessian culture at sites on the opposite bank of the river.