The Tartessian (proto Tartessian, Tartessian and Tartessian-Orientalizing) culture is a well known stage of Iron Age Southern Iberia, however the semi-mythical city of Tartessos (Tarshish in the Bible), allegedly destroyed by the Phoenicians, has never been located, so the understanding of this civilization is lacking the cornerstone.
For long people has speculated that it might been hiding in the marshes of Doñana, a national park at the Low Guadalquivir river. However archaeological research in the area has been nil so far. Until now.
Some years ago aereal photos showed rectangular and circular structures in the marshes that must have been man-made. Now finally researchers of the Spanish Higher Council for Scientific Research (CSIC) are digging the area.
No results have been presented so far but the fact that there is an ongoing excavation is at least assuring.
Source: Telegraph (via Archaeology in Europe).
Note: I would totally disregard the speculations regarding "Atlantis" in the article, specially those related to that pseudocientific Cuban so-called archaeologist, who has no real cue and has been forging artifacts to make his Atlantean claims more appealing to the people he gets donations from.
In my opinion, the legend of Atlantis, as well as the Heraklean one on Erythia, must refer to the slightly better known Portuguese culture of Vila Nova de Sao Pedro and particularly its long living and large capital of Zambujal, many of whose characteristics resemble Plato's description, including that it had a large canal of about the dimensions stated by the Greek philosopher connecting it to the Atlantic Ocean. If I'm correct, then the events reflected in these two legends should have happened in the Bronze Age, when Greek (Mycenaean) influence in SE Iberia is more apparent (later Phoenicians would have the main role). Also the critical role of tin in this period would have been a major drive in whatever conflicts happened in the "far west" (the Hesperides), where the most important sources of this strategic metal used to be (Galicia, Cornwall).
Tartessos belongs to a later phase, surely taking the role of the ill-fated Zambujal and El Argar civilizations for some centuries before its own destruction (by Phoenicians, according to their own claims). Its legacy was nevertheless long-lasting, an is believed that the Turdetani living in the Guadalquivir basin were its cultural descendants.
For a wider review of Ancient Iberia, check my old article on this matter at All Empires.