Routine building work in southern Spain unearthed a very unexpected find this week, when over 600kg of Roman coins were discovered.
The find is "unique in Spain and perhaps the world" experts said of the coins, which were stored in 19 Roman amphoras or earthenware jars.
"We have a team looking into the discovery right now, We believe it is hugely important and will have more information very soon," said a spokesman at Andalucia's Ministry of Culture in Seville told The Local on Thursday.
The coins are currently being examined by experts at Seville's Archeology Museum.
"It is a unique collection and there are very few similar cases," Ana Navarro, head of Seville's Archeology Museum which is looking after the find, later told a news conference.
Navarro declined to give a precise estimate for the value of the haul, saying only that the coins were worth "certainly several million euros".
"The majority were newly minted and some of them probably were bathed in silver, not just bronze," said Navarro.
"I could not give you an economic value, because the value they really have is historical and you can't calculate that."
The coins which date from the late third and early fourth centuries, were unearthed by construction workers working on the mains supply close to Zaudín Park in the town of Tomares, Seville.
They feature the figure of an emperor on the front and on the back, several Roman allegories.
Researchers said they had never seen such an abundant - or homogenous - haul.
The coins, experts revealed, were most probably never in circulation, as they show little evidence of wear and tear, while the containers were smaller than the ones usually used to transport wine and grain and seem specially designed to hold the money.
Experts think the coins may have been part of a tax collection or levies paid to the army.
Spain has a rich Roman history; the country even takes its name from the Roman word Hispania.
The Romans left behind some of Spain's most striking architecture, such as the Tower of Hercules in Galicia, the world's oldest Roman lighthouse still in use, and the Aqueduct of Segovia.