Hamina fortress is a very rare circle fort, representing the Renaissance ideal city embodied by Palmanova city in Italy. It was built after Great Northern War to the ruins of Vehkalahti town.
After Treaty of Nystadt border between Sweden and Russia was moved to Kymeenlakso area in Finland. The construction of the fortress started began by Swedish general Axel von Löwen in 1720s. Protected by six bastions of the fortress the garrison was responsible for defending the city and the coastal road. When next war began in 1741 Hamina fortress was still uncomplete. It was conquered by Russian forces and in new peace treaty fortress left to the Russia side of border.
Russians continued fortress construction in the command of general Aleksander Suvorov. It was part of the South-Eastern Finland fortification system, which was implemented to defence St. Petersburg against western enemies. In the beginning of the 19th century Hamina fortress was outdated and it was reconstructed by the Dutch general Jan Pieter van Suchtelen. When Russia conquered Finland in the Finnish war in 1808-1809 fortress lost its military status. It was abandoded in the 1830s and tsar Nikolai I gave it as the property of Hamina city. During the Crimean war in 1853-1856 fortress reinforced again to fight against the British and French fleet.
Restoration was started in 1957. Much of the fortress remains to this day, and it is used as a venue for different events. Parts of the fortress are still in military use, as the Finnish Reserve Officer School is located in the fortress.
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.