The exact date of Altenburg Castle construction is unknown, however the traditional date given is during the reign of Valentinian I or around 370. The discovery of several small coin hoards near the ruins may indicate a construction date as early as the beginning of the 4th century AD.
The castle was built on a point above the Aar river as part of the Limes Germanicus to protect an easily fordable stretch of the river. The walls were 3–5 m thick and protected by six or eight half-round towers. Nothing is known about the number, location or purposes of the interior buildings.
The Schlössli was built in the ruins of the Roman castle during the late 10th century, probably for an ancestor of the famous Habsburg family. It remained the seat of that family until the construction of Habsburg Castlein the 11th century. After that time it became the seat of Habsburg bailiffs or knights. In 1397 the castle, village and the rest of the Habsburg Eigenamt were gifted to Königsfelden Monastery in Windisch.
On 16 November 1414, Emperor Sigismund called the Council of Constance to settle the Western Schism between the three popes (Benedict XIII, Gregory XII, and John XXIII), all of whom claimed legitimacy. Frederick IV of Habsburg sided with John XXIII. When John XXIII was declared an antipope, he fled the city with Frederick's help. The emperor then declared the Habsburg lands forfeited and ordered the neighboring countries to conquer those lands for the emperor. The city-state of Bern had already pledged their support of the emperor against the Habsburgs in 1414, and so they were ready to invade. Following a series of Confederation victories, in 1415 much of the Eigenamt including Altenburg was in Bernese hands. After Bern assumed control, the monastery retained most of their rights to the land and castles.
In 1528 Bern adopted the new faith of the Protestant Reformation and quickly seized and secularized all of the lands of the religious houses. Under Bernese rule, the castle remained a minor manor house tucked away in the country. During the 16th century a late Gothictower house topped with crow-stepped gables was added. In 1941 it was converted into a youth hostel, which it remains today.References:
Narikala is an ancient fortress overlooking Tbilisi, the capital of Georgia, and the Kura River. The fortress consists of two walled sections on a steep hill between the sulphur baths and the botanical gardens of Tbilisi. On the lower court there is the recently restored St Nicholas church. Newly built in 1996–1997, it replaces the original 13th-century church that was destroyed in a fire. The new church is of 'prescribed cross' type, having doors on three sides. The internal part of the church is decorated with the frescos showing scenes both from the Bible and history of Georgia.
The fortress was established in the 4th century and it was a Persian citadel. It was considerably expanded by the Umayyads in the 7th century and later, by king David the Builder (1089–1125). Most of extant fortifications date from the 16th and 17th centuries. In 1827, parts of the fortress were damaged by an earthquake and demolished.