Pustý hrad Pustý hrad is a castle whose ruins are located on a forested hill in the southern part of Zvolen in central Slovakia . With an area of 76 , 000 m² it is arguably one of the largest medieval castles in Europe . The original name was Zvolen Castle or Old Zvolen ; " Pustý hrad " ( meaning " deserted castle " ) is a much later name used to distinguish the ruin from the present - day Zvolen Castle . Pustý hrad consists of two parts , the Upper Castle and the Lower Castle . The strategic hill site upon the river Hron attracted settlers as early as the late Stone Age ( Baden culture ) . A stone - earth wall discovered in 2009 under the western line of medieval fortification included shreds of pottery from the late Stone Age inside its filling . Research carried out at the Upper Castle in 1992 – 2008 by Václav Hanuliak also identified stone walls built during the Bronze Age and the Iron Age . Excavations have unearthed many precious prehistoric artifacts , including several big bronze treasures of the Lusatian culture , fragments from the Kyjatice culture , and even pottery imported from the Roman Empire . The subsequent Slavic medieval castle was founded in the 9th century . As a regional center , Pustý hrad was incorporated into the Kingdom of Hungary and it became a seat of Zólyom County . The oldest stone buildings ( for example the keep ) are attributed to King Béla III of Hungary . The keep from the 12th century is located at the highest point of the hill - at an elevation of 571 m above sea level - and was once 50 meters high . In the 13th century , an exceptionally large area of the present castle was fully fortified by the royal stonemason master Bertold in order to protect eventual refugees from Zvolen in case of a Mongol invasion . Both the Upper ( 3 . 5 Hectare ) and the Lower ( 0 . 65 ha ) Castle were surrounded by massive fortifications and a 206 metre long defense wall was erected in the saddle below the Lower Castle . In addition to an older keep , another one was built around the same time . Its dimensions of 20 by 20 meters made it one of the largest residential buildings in Central Europe at that time . Pustý hrad was first mentioned in written sources at the beginning of the 13th century , in the chronicle " Gesta Hungarorum " . Subsequent development was connected with counts Demeter and Donč from the Balaša family . Magister Knight Donč was a noble warrior and diplomat serving to Charles I of Hungary . Under the influence of his journey to France , Donč built a significant extension in the Lower Castle and ordered a Gothic modernization . During that phase a four - storey tower was added to the entrance gate of the Upper Castle . A palace , a water tank , a terraced courtyard and other newly constructed buildings in the northern panhandle of Pustý hrad formed what is now known as Donč ' s Castle . The castle lost its importance in the 15th century , the period of military conflicts between John Hunyadi and John Jiskra of Brandýs . Pustý hrad was ruined by fire during a siege in 1452 , probably burnt down by John Hunyadi ' s troops . The last building constructed on the site was a watchtower erected in the second half of the 16th century . Systematic excavations have been conducted since 1992 . Some parts of the castle have been recently reconstructed and the site is easily accessible from Zvolen .