Šariš Castle is a ruined hilltop fortress above Veľký Šariš, northwest of Prešov. The climb is the attraction as much as the masonry: you leave the town edge, work up through the hill, and suddenly get wide views over the Šariš countryside.
The ruins are extensive enough to feel like a proper destination, not just a viewpoint with a wall fragment. Bring water and decent shoes, and allow time to wander the enclosure rather than treating it as a quick photo stop.