According to Hubert Kowalski, a professor at the University of Warsaw, the finds include a 200 kg fragment of an arcade arch, believed to be part of the monumental staircase of the palace built for King Władysław IV Vasa, who ruled Poland from 1632 to 1648.
The Villa Regia was plundered during the Swedish invasion of 1656, with many interior fragments shipped down the Vistula towards the Baltic port of Gdańsk and then on to Sweden. Some boats carrying the loot were deliberately sunk by retreating Swedish forces.
Researchers say the latest discovery will allow for a faithful reconstruction of the staircase, which is expected to feature in the core exhibition of the Museum of Polish History, now under development.
The museum says more than 20 tonnes of architectural relics and artefacts have been recovered from the Vistula riverbed since the project began in 2011.
Deputy Director Krzysztof Niewiadomski said a reconstructed Villa Regia will form a central part of the museum's section highlighting the glory and prosperity of the Polish-Lithuanian Commonwealth, once one of Europe’s largest states, which existed from 1569 to 1795.
(mk/gs)