The first palisade fortress was built in 1545 on the left bank of the Nitra River as part of the line of defense against the Turks. The second fortress, which was built between 1573 and 1580, was one of the most significant Renaissance fortresses in Europe, based on the architectural plan of the Italian brothers Giulio and Ottavio Baldigara. Its floor plan was regular hexagonal, with a regular perpendicular street network and a central rectangular space in its interior. It had six bastions: the bastions of Forgách, Czech, Ernő, Császár, Frigyes and Zserotin. The castle was occupied by the Turks in 1663 and ruled until 1685, its recapture was a celebration of great significance throughout Europe, and bells rang throughout Europe at the direction of the Pope.
The fortress of Nové Zámky was demolished in 1724, but its floor plan can also be found in the coat of arms of the city.
Significant events related to the history of the city are recorded on bronze plaques placed in chronological order on the pavement of the pedestrian street leading to the Main Square.