Controlling the valley leading into Split, this imposing fortress spreads along a limestone bluff, reaching 385m at its highest point. Its long and narrow form (304m by 53m) derives from constant extensions over the course of millennia. Inside, you can clamber all over the fortifications and visit the small museum, which has displays of swords and costumes and detailed information on the castle's brutal past.
Klis' real history (in a nutshell) 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.
Klis is located 12km northeast of the city centre, and can be reached by city bus 22 (13KN) from Trg Gaje Bulata or Split's local bus station.