The River Danube is the second-longest river in Europe, which was known to the ancient Greeks as ‘Istros’. It rises in Germany’s Black Forest and after passing through many countries, including four capital cities, it eventually empties into the Black Sea.
A number of researchers have associated the river with Plato’s Atlantis. One of the earliest was Nicolae Densusianu who proposed that Atlantis had been situated in ancient Dacia, his native Romania. Over a century later some of his ideas have been revived by other Romanian commentators such as Adrian Bucurescu and Alexandra Furdui, who also translated Densusianu’s monumental work into English.
Densusian’s nationalism is now frowned upon and there is an understandable suspicion that his modern Romanian supporters may have similar underlying motivations.
There is a gorge on the Danube known as the Iron Gates which provides part of the boundary between Serbia and Romania. Densusianu located the Pillars of Heracles at the Iron Gates, an idea supported by Ticleanu, Constantin & Nicolescu at the 2008 Atlantis Conference, who place Atlantis further west on the Pannonian Plain [750.365]. In 2020, Veljko Milkovic also placed the ‘Pillars’ at the Iron Gates on the Danube and Atlantis in the Pannonian Basin(c) in his book Panonska Atlantida .
However, Ranko Jakovlievic expressed the view that the Iron Gates section of the Danube was the location of Atlantis!
Related to this, is the claim by an anonymous ‘Sherlock’ that Pindar’s Olympian Ode 3 suggested that the Pillars of Herakles had been situated at the confluence of the Seva and Danube rivers near modern Belgrade(b).
A recent book  by Antonije Shkokljev & Slave Nikolovski–Katin also recount an ancient version of the ‘Labours of Hercules’ that took place in the Balkans.
Christian and Siegfried Schoppe locate Atlantis east of the Danube Delta on Snake Island (Zimiinyi) in the Black Sea, an idea now adopted by George K. Weller(a). [Zimiinyi, Ukrainian territory, was occupied by the Russians 25.02.22 as part of their invasion of Ukraine]