...by Tiberius Haterius Callinicus. I read this weather-beaten inscription on a stone altar at the lapidary of the Aquincum Museum in Budapest (image on the left). People from the antiquity worshipped the Danube river as a God - I first read about this in a József Révay book (Walks in the roman Hungary, 1965) Besides carving altars for the river-god, they proudly named their children after it. Danuvius, son of Diassumarus is known from a stele, erected next to the Danube, and there was a Caius Retonius Danuvius, a pontifex of the emperors cult in Aquincum.
The Danube, as a deity existed earlier, in the Hellenic era too. Its name was Istros (Ιστριη), which meant strong and swift mediated from Thracian language. Istros was the river-god of the north and Scythia according to the Greek mithology. His parents were Oceanos and Tethys, his brothers were the Nile, Eridannus (Po) and Alpheus (Alfíos on the Peloponnesos)
Istros used to be the name of the lower section of the Danube, from the Iron Gates to the Delta. There was also a greek colony with the same name Istros south from the Delta, founded by Miletian merchants and settlers. Some say, thet Istros has a common root with Isar (German), Isére (French), Isarco (Italian) and the slav Bistrica. I’m not sure if it is true, but Greeks do not use this form for the Danube anymore.