Of the many sights hidden high up in the hills above Budva, Kosmač Fortress is perhaps the impressive. A fine example of functional mid-19th century military architecture, it was built during the 1840s along what was then the border between the Austro-Hungarian Empire and Montenegro, and was the most important and strategically placed of the chain of defensive fortifications in the area - receiving a personal visit from Emperor Franz Joseph himself in 1875. Constructed from grey limestone dug out from local quarries, the fortress still blends in quite seamlessly with the rugged rocky terrain. Nowadays the structure is in a state of disrepair that could even be called ruins (as it's missing its roof and significant portions of its tower and walls), but it is still a visually stunning specimen with breathtaking views. 

link: http://www.inyourpocket.com/montenegro/budva/Sightseeing/Around-Budva/Kosmac-Fortress_103235v