The town of Polonne has been known since the times of Kyivan Rus, but it came into the possession of the Ostroh princes only in 1494. The Grand Duke of Lithuania Alexander Jagiellon handed over the town to Prince Kostiantyn Ivanovych Ostrozkyi. However, the prosperity of the town got under way only after Polonne was passed to the possession of Prince Vasyl-Kostiantyn Ostrozkyi. The prince erected a wooden castle over stone foundations in Polonne. Some walls may have been made of brick, but the description of the first third of the 17th century mentions only wooden structures.