Zalavár is a village in Hungary, located in the Zala county. It is located around 9 km (6 mi) southwest of the Lake Balaton.
It was known as 'Mosapurc' in the 9th century, "Mosapurc regia civitate". It was also known as Moosburg and Blatengrad in medieval records. The medieval settlement is known in modern sources as Blatnohrad (Slovak), Blatnograd (Croat), Блатноград (Bulgarian). Ján Kollár called it Salavár in his travel book and described the state of the ruins in 1841.
Remains of the Romanesque basilica in Zalavár
In the 9th century, Moosburg was a fortified settlement built at the Zala river and was a capital of the Frankish vassal Balaton Principality ruled by a Slavic prince Pribina ("Privinae civitas, munimen, castrum in nemore et palude Salae" in a Salzburg chronicle). During the reign of Pribina's son, prince Kocel (861-876), in the summer of 867, it provided short-term hospitality to brothers Cyril and Methodius on their way from Great Moravia to the pope in Rome to justify the use of the Slavonic language as a liturgical language. They and their disciples turned Blatnograd into one of the centers that spread the knowledge of the new Slavonic script (Glagolitic alphabet) and literature, educating numerous future missionaries in their native language.
Battle of Pressburg 
Historians claim that Urbs Paludarum, Brazlavo's burg (Moosburg), was the place of Battle of Pozsony instead of Bratislava. The only contemporary source mentioning a location of the battle is the Annales Iuvavenses maximi (Annals of Salzburg); however, the reliability of these annals is questionable, as they survive only in fragments copied in the 12th century. They state that the battle took place in the vicinity of Brezalauspurc, the castle of Duke Brazlavo, located west of Lake Balaton.
- ^ Charles R. Bowlus, Franks, Moravians, and Magyars: the struggle for the Middle Danube, 788-907, University of Pennsylvania Press, 1995, p. 220
- ^ Richard A. Fletcher, The Barbarian Conversion: From Paganism to Christianity, University of California Press, 1999, p. 348
- ^ Bowlus, Charles R. (1995). Franks, Moravians, and Magyars: The Struggle for the Middle Danube, 788-907. pp. 258-9.
- ^ Timothy Reuter, Germany in the Early Middle Ages 800–1056 (New York: Longman, 1991), 138–139.
- ^ Bowlus, Charles R. (2006). The battle of Lechfeld and its aftermath, August 955: the end of the age of .... p. 83. ISBN 9780754654704.