Visegrád is famous for the remains of the Early Renaissance summer palace of King Matthias Corvinus of Hungary and the medieval citadel. Upper castle - After the Mongol invasion, King Béla IV of Hungary and his wife had a new fortification system constructed in the 1240-50s near the one destroyed earlier. The first part of the new system was the Upper Castle on top of a high hill. The castle was laid out on a triangular ground plan and had three towers at its corners. In the 14th century, at the time of the Angevin kings of Hungary, the castle became a royal residence and was enlarged with a new curtain wall and palace buildings. Around 1400 King Sigismund had a third curtain wall constructed and enlarged the palace buildings. At the end of the 15th century, King Matthias Corvinus had the interior renovated. The Upper Castle also served for the safekeeping of the Hungarian royal insignia between the 14th century and 1526. In 1544 Visegrád was occupied by the Ottoman Empire, and, apart from a short period in 1595-1605, it remained in Turkish hands until 1685. The castle was seriously damaged by the Turks and was never used afterwards. The castle is now open to the public to visit.