Hakoinen Castle was an ancient hill fortification, but nowadays there's only some ruins left. Dated medieval, the fortification was situated on a very steep rock by lake Kernaala (Kernaalanjärvi) reminiscent of a hill fort tradition. The top of the rock is 63 meters above the water level in the lake. Today very little remains of the castle. Equally little is known about its origins. One postulation is that it was built by the Swedes as their original stronghold in the medieval Häme area.
The castle was probably built at the end of the 13th century or during the early 14th century. It has been speculated that Hakoinen might have been the fort that was attacked by invading Novgorodian forces in 1311 during the Swedish-Novgorodian Wars, as described in the Novgorod Chronicle.
Eventually Hakoinen was left out of use. Some activity seems to have remained there until 1380s. The castle rock was later a part of a large estate belonging to the bailiff of Häme Castle. According to excavations, the castle was divided into two parts. Lower defensive constructions were mostly made of wood. Constructions on the rock were made of bricks and rocks. The castle probably had one tower.
Although very little remains of the castle, the medieval flora and huge sights from the top of the hill makes Hakoinen castle hill interesting place to visit.
Hochosterwitz Castle is considered to be one of Austria's most impressive medieval castles. The rock castle is one of the state's landmarks and a major tourist attraction.
The site was first mentioned in an 860 deed issued by King Louis the German of East Francia, donating several of his properties in the former Principality of Carantania to the Archdiocese of Salzburg. In the 11th century Archbishop Gebhard of Salzburg ceded the castle to the Dukes of Carinthia from the noble House of Sponheim in return for their support during the Investiture Controversy. The Sponheim dukes bestowed the fiefdom upon the family of Osterwitz, who held the hereditary office of the cup-bearer in 1209.
In the 15th century, the last Carinthian cup-bearer, Georg of Osterwitz was captured in a Turkish invasion and died in 1476 in prison without leaving descendants. So after four centuries, on 30 May 1478, the possession of the castle reverted to Emperor Frederick III of Habsburg.
Over the next 30 years, the castle was badly damaged by numerous Turkish campaigns. On 5 October 1509, Emperor Maximilian I handed the castle as a pledge to Matthäus Lang von Wellenburg, then Bishop of Gurk. Bishop Lang undertook a substantial renovation project for the damaged castle.
About 1541, German king Ferdinand I of Habsburg bestowed Hochosterwitz upon the Carinthian governor Christof Khevenhüller. In 1571, Baron George Khevenhüller acquired the citadel by purchase. He fortified to deal with the threat of Turkish invasions of the region, building an armory and 14 gates between 1570 and 1586. Such massive fortification is considered unique in citadel construction.
Since the 16th century, no major changes have been made to Hochosterwitz. It has also remained in the possession of the Khevenhüller family as requested by the original builder, George Khevenhüller. A marble plaque dating from 1576 in the castle yard documents this request.
A specific feature is the access way to the castle passing through a total of 14 gates, which are particularly prominent owing to the castle's situation in the landscape. Tourists are allowed to walk the 620-metre long pathway through the gates up to the castle; each gate has a diagram of the defense mechanism used to seal that particular gate. The castle rooms hold a collection of prehistoric artifacts, paintings, weapons, and armor, including one set of armor 2.4 metres tall, once worn by Burghauptmann Schenk.