The baroque-classic palace of primate Michal Poniatowski, the brother of Polish king – Stanislaw August Poniatowski. It was erected by Dominik Merlini in 1775-1779 and remodeled by Henryk Marconi in 1837. The Palace is surrounded by the park designed in 18th century, with romantic buildings: Chines House, conservatory and recluse cave. The interiors of the palace are very rich, e.g. with paintings of Szymon Mankowski and Antonio Tavelli, and stucco works of Antono Bianchi. September 1939, the palace was headquarters to "Modlin" Army.
Nowadays, the palace-park complex in Jablonna is conference and training venue.
