Construction workers have uncovered a trove of Roman-era artifacts in the Andalusian town of Tomares, in Seville province.

The find, which archeologists are already calling unique to Spain and possibly the world, includes 19 amphorae containing around 600 kilograms of bronze coins dating back to the 4th century AD.

The coins depict an emperor on one side and various Roman allegories on the back, including abundance. Researchers insisted that never before had so many homogeneous coins been found together.

Investigators also noted that the coins, which were probably minted in the East, were never in circulation and are thus not worn out by use, the news agency Efe reported.

The amphorae, some of which were broken and others whole, are not of the type commonly used to transport grain or wine. These smaller containers were all inside a storage space that had been sealed and covered with broken items.

This treasure was “deliberately concealed underground and covered with a few bricks and ceramic filler,” according to sources at the Andalusian department of culture and quoted by the news agency Europa Press.

Investigators are working with the initial hypothesis that the money was meant to pay imperial taxes or army levies.

The coins have already been transferred from Tomares (population 24,000) to the Archeology Museum of Seville.

Tomares city planning councilor Lola Vallejo, of the Popular Party (PP), said that the find was a one-off event and that the work to bring a water supply line to the park are proceeding “as normal.”

In statements to Europa Press, Vallejo said that operators working for the city and the Guadalquivir Water Confederation noticed irregular terrain inside one of the ditches, barely one meter below ground level.

All work was “brought to a halt” and workers uncovered the amphorae.

At that point, “the protocol for these cases was activated,” said Vallejo. The Civil Guard and archeologists working for the Andalusian government were called in, and the latter asked for the ditch to be widened.

“The process ended in late afternoon and we were told that it was a one-off find, so work will proceed today as normal,” added the councilor.