Birtvisi is a ruined medieval fortress in Kvemo Kartli, Georgia, nested within limestone cliffs in the Algeti river gorge. It is now within the boundaries of the Tetri-Tsqaro municipality, adjacent to the Algeti National Park.
Birtvisi is essentially a natural rocky fortress of 1 km², secured by walls and towers, the most prominent of which – known as Sheupovari ('Obstinate') – tops the tallest rock in the area. Various accessory structures, an aqueduct included, have also survived.
In written sources, Birtvisi is first mentioned as a possession of the Arab amir of Tiflis of which he was divested by the Georgian nobles Liparit, Duke of Kldekari and Ivane Abazasdze in 1038. In medieval Georgia, Birtvisi entertained a reputation of an impregnable stronghold whose master could control the entire strategic Algeti gorge. The Turco-Mongol amir Timur notably reduced the fortress during one of his invasions of Georgia in 1403. After the partition of the Kingdom of Georgia later in the 15th century, Birtvisi was within the borders of the Kingdom of Kartli and in possession of the princes Baratashvili.
References:Visby Cathedral (also known as St. Mary’s Church) is the only survived medieval church in Visby. It was originally built for German merchants and inaugurated in 1225. Around the year 1350 the church was enlarged and converted into a basilica. The two-storey magazine was also added then above the nave as a warehouse for merchants.
Following the Reformation, the church was transformed into a parish church for the town of Visby. All other churches were abandoned. Shortly after the Reformation, in 1572, Gotland was made into its own Diocese, and the church designated its cathedral.
There is not much left of the original interior. The font is made of local red marble in the 13th century. The pulpit was made in Lübeck in 1684. There are 400 graves under the church floor.