During the so-called Deluge during the Great Northern War of 1655-60, Swedish King Karl X Gustaf held Warsaw under siege and looted its treasure chests completely, loading his booty onto ships that, via Gdansk, would carry the swag to Sweden.
“The Swedes plundered everything,” said professor Hubert Smith from the archaeological department of Warsaw University, during a press conference, reports daily Dagens Nyheter.
However, not all of the booty-carrying ships made it to their intended destination.
“Some of them simply sunk,” said archaeologist Dr Hubert Kowalski, one of the scientists behind the project, in an interview with Polish Radio, according to polish news site The News.
The vessel found at the bottom of the river is believed to be one of those that were lost.
The project to retrieve the ship was launched in 2008 and scientists have been using state of the art technology to scan the riverbed.
Among the findings are marble relics with the coat of arms of the Vasas, according to the site.
Kings of the Swedish Vasa dynasty ruled Poland for more than 80 years; Sigismund III Vasa from 1587 to his death in 1632 and then his sons Vladislav V 1632-1648 and Johan II Kasimir 1648 to 1668.
Despite being king of Sweden between 1592 and 1599, Sigismund had been deposed of the throne by his uncle Karl IX.
Although it is not clear how much treasure the Swedes took from Poland during the war, the saying goes that after the soldiers had left, not one silver spoon could be found in the manor houses of the Polish countryside, according to the site.
The scientists have so far found 70 separate items, in the form of five tonnes of sculptures, decorations, doors, and even pieces of floors at the bottom of the river, and the researchers are confident there is more to be discovered.
Scientists believe that these relics are from the Royal Palace in Warsaw and the former Villa Regia, which was later transformed into the Kazimierzowski Palace.
According to local media, the findings will be displayed in the Warsaw Historical Museum.