Danube.
Danube River
Danube River
The southernmost border was the one between southern Egypt ad Numidia
The Snake River forms part of Oregon's eastern border
The Mississippi River forms most of Arkansas's eastern border.
The Black Sea forms a small portion of the Eastern border of Europe. The Mediterranean is also part of the Southeastern border.
The Atlantic Ocean forms the eastern and southern border of New England.
The Atlantic Ocean forms most of the eastern border of these regions.
Eastern Border
Georgia's eastern border is the Atlantic Ocean
The Caspian sea forms Azerbaijan's eastern border.