The remains of the fortress can be visited
Fortress of Klis

Klis Fortress, a medieval complex, is above the village of the same name in Dalmatia, near Split in Croatia. Its strategic location made it a stronghold that guarded the frontier for centuries and was contested multiple times.
History+
The fortress's origins trace back to an Illyrian tribal stronghold. In the 9th century, Klis became the seat of Duke Mislav of Croatia and later the residence of many Croatian rulers, including Duke Trpimir I, who expanded the fortress. In March 1242, the Tatars suffered a defeat here while pursuing King Béla IV of Hungary.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://en.wikipedia.org/wiki/File:Klis_0807_3.jpg
This description draws on the facts documented in the linked Wikipedia article; Wikipedia content is licensed under CC BY-SA 4.0. Wording and editing: Mobile History.
Location: 43.5598, 16.5229