Arévalo castle was built in the 14th century and reformed during the 15th and 16th centuries. It has a pentagonal ground plan and a large Tower of Homage. Inside there is a Cereal Museum.
King Pedro I, the Cruel, locked his wife Blanca de Borbón in the castle. Juan II and Enrique IV possessed it, the latter handed it to don Álvaro de Zúñiga; between 1476 and 1480, Zúñiga and the Catholic Monarchs negotiated a compesation for Arévalo and, in the ends, the village was taken over by the Crown. Subsequently it became a state prison.
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.