In the absence of electronic communications and motorized transportation, the Romans built a vast empire that connected different parts of the globe. The north side crosses 56° north latitude and the south side goes down past 2 north latitude

In the absence of electronic communications and motorized transportation, the Romans built a vast empire that connected different parts of the globe. The north side crosses 56° north latitude and the south side goes down 24° north latitude. "Of the geographically contiguous empires of pre-modern history, only the Mongols, the Incas, and Tsarist Russia were able to reach or surpass Rome's north-south dominance." Only a handful of empires controlled large areas from mid-to-high latitudes to the tropical edge, and the longevity of Rome was unique.

The northern and western parts of the Empire were under the control of the Atlantic climate. The Mediterranean Sea was the ecological center of the empire. The fragile, moody nature of the Mediterranean climate – relatively moderate temperatures, dry summers, and wet winters – makes it a unique climate. The dynamic mechanism of a huge inland sea, combined with the rugged inland terrain, has created an extremely diverse climate in a small area. In the border areas of the southern and eastern parts of the empire, subtropical high pressures prevailed, turning the land into a quasi-desert and then a real desert. Egypt, as the breadbasket of the empire, introduced the Romans to a completely different climatic mechanism: rainwater from the monsoon fell on the Ethiopian plateau, creating a life-giving flood of the lower Nile. It was all under roman rule.