Unknown Soldiers Podcast Episode #42, "Give Me Back My Legions", Maps and Sources
The Roman Empire under Augustus Caesar. Look at the gray area beneath Denmark, you can see Arminius's coalition and the Battle of the Teutoburg Forest.
Rough (very rough) location of the short-lived Roman province of Germania.
Solid close-up of Germania. The yellow is "Roman Germany," the dotted red line is the Roman frontier after the Varus disaster. You can see Varus's rough line of march along that red arrow heading towards Kalkriese.
The final Teutoburg Battle near Kalkriese.
Davis, Paul K. 100 Decisive Battles: From Ancient Times to the Present. New York: Oxford University Press, 2001.
Goldsworthy, Adrian. In the Name of Rome: The Men who Won the Roman Empire. New Haven, CT; Yale University Press, 2016.
McNally, Michael. Teutoburg Forest, AD 9: The Destruction of Varus and His Legions. Oxford: Osprey Publishing, 2011.
Murdoch, Adrian. Rome's Greatest Defeat: Massacre in the Teutoburg Forest. Cheltenham, UK: The History Press, 2012.
Wells, Peter S. The Battle That Stopped Rome: Emperor Augustus, Arminius, and the Slaughter of the Legions in the Teutoburg Forest. New York: W.W. Norton & Company, 2003.