Treasures that apparently were stolen from Poland by Swedish invaders in the 17th century were revealed on the riverbed of Warsaw’s Vistula, dried due to a severe summer drought which had Poland's longest river, to its lowest level since regular records began 200 years ago.

Police are working with archaeologists to recover priceless, gigantic carved marble and alabaster elements used in the columns, fountains, and staircases of Polish palaces, which were robbed from Warsaw's royal residences by the Swedes who overran the nation in mid-17th century.

Archaeologists believe a huge cargo of stonework sank to the bottom of the Vistula while it was being carried by a barge that was heading to the Baltic Sea and further to Sweden.