Spanish police have arrested 52 people and seized 300,000 archaeological artefacts they describe as "of great historic and economic value".
Smaller items were sent through the post to collectors
Officers say the items were seized in 68 raids across Spain at 31 sites of Iberian, Roman, Visigoth and Arab cultures.
The raids uncovered objects like bronze statues, ancient coins and columns from digs across the south.
Police say some items had been taken abroad via an Italian intermediary.
According to the police, 30 of those arrested were thieves who would use metal detectors, maps, manuals and other tools to go on treasure-collecting trips.
The majority of the archaeological sites plundered were in Seville province, which has Roman and Moorish history.
Others were in Cadiz, Huelva, Jaen, Malaga and Badajoz.
Nine of those detained were "collectors", while 13 were presumed accomplices.
Around 200 officers took part in the operation, which began after an investigation uncovered a group of people smuggling historical objects from undersea sites in the Gulf of Cadiz.
The thieves would send small items such as coins through the post, said the police.
Larger pieces destined for Faro in Portugal were also found, from where they were to be flown to Belgium.