The remains of the Castle can be visited
Bijela Tabija Fortress

The Bijela Tabija fortress, also known as the White Fortress, is a national monument of Bosnia and Herzegovina. It forms a part of the former city wall of Vratnik and once guarded the eastern access to the city.
History+
The exact time of the fortress's construction is debated. One theory suggests that Bijela Tabija was built around 1550, based on reports by the traveler Katarino Zeno, and was later replaced by a new fortress during the construction of the city of Vratnik. Another view suggests that a fortress already existed on this site in the Middle Ages, no larger than typical defensive structures protecting open settlements. Given the confirmation of a medieval settlement called Tornik in present-day Sarajevo, it is plausible that it possessed a protective fortress.
Source: Wikipedia · Licence: CC BY-SA 4.0 · Image: http://en.wikipedia.org/wiki/File:Bijela_tabija_2009.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: 43.8594, 18.4446