Klis' real history goes like this: founded by the Illyrians in the 2nd century BC; taken by the Romans; became a stronghold of medieval Croatian duke Trpimir; resisted attacks for 25 years before falling to the Turks in 1537; briefly retaken in 1596; finally fell to the Venetians in 1648. Game of Thrones fans will probably recognise the fortress as Meereen, where Daenerys Targaryen had all those nasty slave-masters crucified in season four. If you're having trouble visualising it, there's a room with stills from the show to jog your memory.