Carnuntum , the main ancient Roman Legion Camp the upper Danube border, located at Petronell, 20 miles (32 km) east of Vienna . It was the base of the Emperor Tiberius in its attacks on the Marcomanni ( 6 n. ), although under Emperor Claudius a fortress for a legion was built for the first time . Built stone structures were then repaired ad 73-76.
In Ad - In 106 it became the capital of the province of Upper Pannonia. Here the emperor wrote Marcus Aurelius second book Meditations during his campaign against the Marcomanni (172–174). The thriving city was destroyed by the Marcomanni but soon rebuilt and had under Septimius Severus regained their prosperity . Here found 308 the conference of emperors Diocletian , Galerius and Maximian instead. The built by them Altar for Mithra is an important historical source. Valentinian I. stayed in Carnuntum in 375 during his campaign against the Germans. The German invasion of 395 signaled the end of Carnuntum and Pannonia was given to the Huns in 433. After that, the historical record of Carnuntum is silent.