Borsh Castle (also known as Sopot Castle) dates from Antiquity, and its fortifications follow the trace of an acropolis, with four subsequent phases of reconstruction, ranging from the early Byzantine period to the late Middle Ages.
The site is first mentioned in the early 13th century, when archbishop Demetrios Chomatenos wrote of the 'archonship of Sopotos', part of the region of Vagenetia. In 1258, the Despot of Epirus Michael II Komnenos Doukas gave the castle along with Buthrotum and the island of Corfu as dowry for his daughter Helena to Manfred, King of Sicily. It came back under Epirote control soon thereafter, before being once again ceded by Nikephoros I Komnenos Doukas to Charles I of Anjou in 1279. The area returned again to Epirote hands in the subsequent decades, but in the Epirote rebellion against Palaiologan Byzantine rule in 1338–39, it remained loyal to Emperor Andronikos III Palaiologos.
Following the Ottoman conquest, a cadaster from 1431 lists Sopot with 60 households, and as capital of a nahiye. In 1456, troops of King Alfonso V of Aragon were operating in the area of Sobato against the Ottomans. In 1470 it was under Venetian control, under the jurisdiction of the governor of Corfu; at the end of the Ottoman–Venetian War of 1463–1479, the Ottomans laid claim to it and apparently received it, for in 1488 the local Albanian population rebelled against Ottoman rule.
The walls of the castle, which follow the ancient fortifications, survive. In the interior, the medieval fortress was divided through a wall in two. Triangular towers were added later, probably during the middle Byzantine period. In the interior of the castle stand ruins of various buildings and cisterns.References:
From its origin as a small stronghold built by the ancient Illyrian tribe Dalmatae, becoming a royal castle that was the seat of many Croatian kings, to its final development as a large fortress during the Ottoman wars in Europe, Klis Fortress has guarded the frontier, being lost and re-conquered several times. Due to its location on a pass that separates the mountains Mosor and Kozjak, the fortress served as a major source of defense in Dalmatia, especially against the Ottoman advance, and has been a key crossroad between the Mediterranean belt and the Balkan rear.
Since Duke Mislav of the Duchy of Croatia made Klis Fortress the seat of his throne in the middle of the 9th century, the fortress served as the seat of many Croatia"s rulers. The reign of his successor, Duke Trpimir I, the founder of the Croatian royal House of Trpimirović, is significant for spreading Christianity in the Duchy of Croatia. He largely expanded the Klis Fortress, and in Rižinice, in the valley under the fortress, he built a church and the first Benedictine monastery in Croatia. During the reign of the first Croatian king, Tomislav, Klis and Biograd na Moru were his chief residences.
In March 1242 at Klis Fortress, Tatars who were a constituent segment of the Mongol army under the leadership of Kadan suffered a major defeat while in pursuit of the Hungarian army led by King Béla IV. After their defeat by Croatian forces, the Mongols retreated, and Béla IV rewarded many Croatian towns and nobles with 'substantial riches'. During the Late Middle Ages, the fortress was governed by Croatian nobility, amongst whom Paul I Šubić of Bribir was the most significant. During his reign, the House of Šubić controlled most of modern-day Croatia and Bosnia. Excluding the brief possession by the forces of Bosnian King, Tvrtko I, the fortress remained in Hungaro-Croatian hands for the next several hundred years, until the 16th century.
Klis Fortress is probably best known for its defense against the Ottoman invasion of Europe in the early 16th century. Croatian captain Petar Kružić led the defense of the fortress against a Turkish invasion and siege that lasted for more than two and a half decades. During this defense, as Kružić and his soldiers fought without allies against the Turks, the military faction of Uskoks was formed, which later became famous as an elite Croatian militant sect. Ultimately, the defenders were defeated and the fortress was occupied by the Ottomans in 1537. After more than a century under Ottoman rule, in 1669, Klis Fortress was besieged and seized by the Republic of Venice, thus moving the border between Christian and Muslim Europe further east and helping to contribute to the decline of the Ottoman Empire. The Venetians restored and enlarged the fortress, but it was taken by the Austrians after Napoleon extinguished the republic itself in 1797. Today, Klis Fortress contains a museum where visitors to this historic military structure can see an array of arms, armor, and traditional uniforms.