The Trsat Castle represents a strategically embossed lookout on a hill 138 meters above sea level dominating Rijeka. It was mentioned as a parochial centre for the first time in 1288. At this same site there was a Liburnian observation post from prehistoric times, used for monitoring the roads leading from the hinterland to the coast.
http://www.visitrijeka.eu/What_To_See/Attractions/Trsat_Castle