Danube once appears as the mother of Vrtra, "a dragon blocking the course of the rivers." The Finnish word for Danube is Tonava, which is most likely derived from the word for the river in Swedish and German, "Donau". Its Sámi name "Deatnu" means "Great River". It is possible that "dānu" in Scythian as in Avestan was a generic word for "river": "Dnieper" and "Dniestr", from "Danapris" and "Danastius", are presumed to continue Scythian "*dānu apara" "far river" and "*dānu nazdya-" "near river", respectively. The river was known to the ancient Greeks as the "Istros" (Ἴστρος) a borrowing from a Daco-Thracian
Source of the Danube above and below Tuttlingen (see also Danube Sinkhole). As a consequence, it dries up most time of the year. Near Ulm, in terms of hydrology, the Danube gets a tributary to the Iller which is more water-rich. It even gets surpassed by the Inn. The Donaubach rises on the castle grounds near the left corner of the front face of the castle Donaueschingen in a karst spring. This karst spring has an embankment of 15 to 70 l/s and enters into the Brigach after flowing 90 meters belowground. The Brigach and the Breg become the Danube after 1.5 km. The