Introduction to the Citadella Fortress: Citadella, the hilltop fortress on the Gehreert Mountain, was built by the Habsburgs in 1851 after suppressing the Hungarian people's war for independence (1848-49). It was built to prevent the revolutionary activities of the people of Budapest. After the Austrians withdrew, it was also used as a barracks for the Hungarian army. In 1894, it was taken over by the city, and now it has become the best place for locals and tourists to climb up and enjoy the scenery.