It is on the site of the citadel, whose civil and military buildings display a remarkable architectural unity, that Osijek developed from the 12C onwards. Left abandoned in the 18C, besieged in 1991, the citadel is now undergoing extensive restoration. The university has taken over many palaces; cafés, restaurants and galleries have settled through the narrow streets. Holy Trinity Square, where the Museum of Slavonia is located, makes a picture perfect scene.