Osijek was restored to western rule on 29 September 1687 when the Turks were ousted and the city was occupied by the Habsburg Empire. Between 1712 and 1715, the Austrian authorities built a new fortress, outer walls and all five planned bastions (authored by the architect Maximilian de Gosseau) known as Tvrđa. It is a unique urban and military complex that lies in the heart of the town.