The Agri Decumates or Decumates Agri ("Decumatian Fields") were a region of the Roman Empire's provinces of Germania Superior and Raetia, covering the Black Forest, Swabian Jura, and Franconian Jura areas between the Rhine, Main, and Danube rivers, in present southwestern Germany, including present Frankfurt, Stuttgart, Freiburg im Breisgau, and Weißenburg in Bayern.
According to the English Classicist Michael Grant, the word probably refers to an ancient Celtic term[4] indicating the political division of the area into "ten cantons."
Tacitus writes that: I should not reckon among the Germanic tribes the cultivators of the tithe-lands [agri decimates], although they are settled on the further side of the Rhine and Danube.
[2] They built a road network for military communications and movements, and improved protection from invading tribes using the region to penetrate into Roman Gaul.
The larger Roman settlements were Sumolecenna (Rottenburg am Neckar), Civitas Aurelia Aquensis (Baden-Baden), Lopodunum (Ladenburg) and Arae Flaviae (Rottweil).