Stegeholm's Castle Ruin is located on Slottsholmen by the mouth of Gamlebyviken. The oldest notes about Stegeholms castle are from the 14th century. It was probably built before 1370 by Albert II, Duke of Mecklenburg (the father of King Albert of Sweden). The castle was destroyed by fire in 1517 and rebuilt in 1521. In 1612 it was conquered by Danish. The final destruction appeared in 1677 when Stegeholm was destroyed by Danish-Dutch fleet. Today Västerviks Visfestival (Song festival) is organized in the castle ruins annually.
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.