The three features are, Rhine River, Dounbe River, and the Carpathians Mts.
They were the rivers Rhine and Danube and the limes Germanicus, a series of fortifications between the two rivers.
Hadrian's Wall, the Rhine River, and the Danube River
Hadrian's Wall in Britain the Danube River in Continental Europe
The Syrian Desert.
Hadrians wall
The three features are, Rhine River, Dounbe River, and the Carpathians Mts. They were the rivers Rhine and Danube and the limes Germanicus, a series of fortifications between the two rivers.
The natural borders in the northern parts of the Roman empire in what can be called "central Europe" were the Rhine and Danube rivers. Incursions by Germanic Tribes for example were an ongoing problem for Rome. In the ending years of the empire, these river boundaries were crossed en mass by barbarians.
mediterranean sea
The western boundary of the Roman Empire was the Atlantic Sea. The eastern boundary was Persia (modern day Iran and central and southern Iraq).
From Libya to Central Asia.
Northern India.
In World War I, the Central Powers consisted of four nations roughly occupying the central portion of Europe and the northern Middle East. From north to south, the nations were Imperial Germany, the Austro-Hungarian Empire, Bulgaria, and the Ottoman Empire.
They took over the Babylonian Empire, then added to it by taking over Asia Minor, Central Asia, The Indus Valley, Libya, Egypt and northern Greece.