Gudsberga Abbey (Gudsberga Kloster) was a Cistercian abbey established in 1486. It was the last Cistercian abbey in Sweden. Gudsberga owned farms, manors, foundries and mines until 1527, when it was reduced to the Crown during Reformation. In 1538 and 1544 King Gustav Vasa ordered to send silver from abbey to Stockholm. It was demolished later. Today some stone foundations remain and there is a museum exhibiting the forge of abbey.
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.