The Odescalchi Castle situated on the west side of the fortified town of Ilok is in fact the reconstructed medieval castle of Nikola Iločki, the croatian viceroy and king of Bosnia.
It was built in the first middle of the 15th century and is the most important residential and representative building in medieval Slavonija and Srijem. The Turks conquered Ilok in the first middle of the 16th century and after the banishing of Turks, in 1697. the Austrian emperor Leopold I. bestowed the castle to Livijo Odescalchi and his familiy in order to compensate for their financial help in the war of liberation and for gratitude to pope Innocent XI. Odescalchi who gathered the european monarchs in the war against Turks.
The castle remains in their property untill 1945. as a summer residence.
The palace of Nikola Iločki was built in the transitional gothic-renaissance style as a four-winged, two-storey fortified citadel with inner courtyard, utility rooms, representative knight hall with vaults, gallery and residential spaces of the king. During the turkish rule the palace was destroyed and neglected and at the end of the 17th century the north wing was demolished as well as all rooms inside the fortification. At the beginning of the 18th century the Odescalchi family begun the renovation: the square conventual plan has been modified, the castle was rebuilt in baroque style and on the courtyard façade of the south wing in all three storeys a passage opened by arcades was built. This passage was originally done in not-plastered bricks which are characteristic for the roman architecture tradition. During the 19th century in the south wing a central staircase with a covered roof-terrace has been constructed, the roof has been repaired and all the façades were integrated in historicistic style which is recognizable for the symmetric disposition of the façade openings, lack of decoration, accentuated cornerstones, stylized ashlar blocks on the ground floor façade, hanging blind arcades beneath the dividing cornice, the dividing cornices of the floors and accentuated window lintels of the first floor.
Today the castle is a three-storey, three winged, U-shaped building facing Danube whose walls, foundations and vaults are built in bricks, while the ceilings and roof truss system are wooden constructions. The roof covering is made by Biber tile. The preliminary conservation-restoration, geomechanical and structural researches on the Odescalchi Castle conducted in 2000. preceded the works on the renovation that is still undergoing. The renovation consists of static improvement of the building (since the building structure caved in as a consequence of water impact), improvement and renovation of the complete roof truss system and sheet-metal material, restoration and reconstruction of the ruined parts of the object, façade renovation and design of the interiors, all in accordance with the conservation terms.