The Co-Cathedral of Saint Nicholas is the dominant church on Hlavná ulica and the best architectural reason to stop in Prešov. Its Gothic mass gives the long main street a proper centre of gravity, and the tower is the landmark you keep returning to while wandering the old town.
Inside, look for the layered feeling common to Central European churches: Gothic structure, later furnishings, and the marks of a town that has been Catholic, Lutheran, royal, and regional at different points in its history. Even a short visit helps explain why Prešov's main street feels more substantial than its modest fame suggests.