The Co-Cathedral of St. Nicholas was built between 1613 and 1662. It was designed between 1610 and 1615 by Agustín Bernardino, a student of Juan de Herrera, and was constructed over an ancient mosque. The older cloister was built originally in the 15th century in Valencian Gothic style.
The cathedral has a Latin cross plan, though the transepts are quite short. Flanking the nave are six interconnecting side chapels and an ambulatory around the apse. A blue dome rises 45 meters above the crossing. The chapel of Holy Communion, configured as a small Greek cross-planned temple, is considered to be one of the most beautiful examples of the Spanish Baroque.
The external appearance of the cathedral is quite sober. The main facade located on the east side is of the Doric order, and the one built on the south side is of Ionic order.
References:Herceg Novi was founded (on a former small fishing village, existing since Roman Empire times) as a fortress in 1382 by first Bosnian King Stjepan Tvrtko I and was called Sveti Stefan or Castelnuovo. The Turks conquered Herceg Novi in 1482, and ruled for 200 years, until 1687. However, there was a short pause between 1538 and 1539 when it was held by the Spaniards before they were defeated in the Siege of Castelnuovo. Turkey ruled again until 1687, from then until 1797, the town was ruled by the Venetian Republic.
The Herceg Novi old town is amazing. It is on a fairly steep hill that leads all the way down to the sea. Wandering through the small stairways to the various plazas and fortresses is a many hour adventure.