The Palace of Omurtag is an archaeological site in northeastern Bulgaria dating to Late Antiquity and the Early Middle Ages located near the village of Han Krum in Shumen Province. The site has been pinpointed as the location of a fort and palace of Omurtag, ruler (kanasybigi) of the First Bulgarian Empire in 815–831, as mentioned in the Chatalar Inscription of 822. Earlier structures in the vicinity of the fortress have been identified as the Arian episcopal see of a Gothic bishop.
The main feature of the archaeological site is the early-9th-century Bulgarian fortified rampart with Omurtag's palace within its limits.
The earliest ruins at the Palace of Omurtag site include four churches, two of which built on top of each other; a bath; and fortified walls, all dating to Late Antiquity (roughly 250–650 CE). Three of the churches and the bath lie outside the medieval fortification, while one of the churches and the traces of ancient walls have been excavated within its limits.
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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.