An imperial supply chain facilitated a sophisticated and diverse Roman economy, especially luxuries for the Roman elite like a thriving silver sector based on raw materials sourced from Britannia and Hispania but worked into ornaments and jewelry in Rome, as well as nearby cities on the Italian Peninsula, and certain special cities like Trier, which were nominally equidistant between Britannia, Hispania, and Rome.

Rome's supply chain was a classic colonial enterprise, based on raw materials sourced from the periphery, and luxury goods crafted by artisans in sophisticated workshops in the center of power; raw materials were most often not constructed into ornaments or jewelry in far flung provinces.

Although a minority of silver may have been given to Egyptian officials in exchange for grain, silver retains value whereas grain is consumed; empires are constructed in the process of expanding control by a center of power, and dumping huge amounts of precious substance like silver into Egypt would increase the power of Egypt instead of Rome itself. The Roman elite would have been careful to keep the majority of silver in their own hands.

Although certain members of the Roman elite may have cared for the orphans of war, Roman authorities wanted silver for luxury goods.

Damascus Steel was a type of metal forged in the Middle Ages, not during the time of Ancient Rome.

Alexandria was the political capital of Egypt at the time, and Egyptian grain, as well as Egypt's navy, were vital to Caesar's attempts at dictatorship.

Sparta was a military power during the Greek Golden Age, a period of well-documented philosophical, architectural, and artistic output.

Athens was a cultural and naval power during the Greek Golden Age, never a major producer of grain.

Carthage was a major antagonist in multiple wars against the Roman Empire.

Troy was a major proponent in the semi-historical Trojan War between the cities of Troy and a league of Hellenes led by Agammemnon.

At the height of its power the Roman Empire effectively controlled the entirety of the Mediterranean. This made trading and sailing relatively efficient and safe (so long as one was a member of the Roman Empire). The Roman navy patrolled the seas and protected traders from the plundering efforts of pirates and rival civilizations.

Silk production had long been a Chinese state secret when a small group of Byzantine monks smuggled silkworms back from China in the sixth century. This led to the breakdown of the Chinese monopoly and the further growth of the Byzantine Empire as the wealthiest in Europe.

The Grand Canal is the longest canal or artificial river in the world. It starts in Beijing and links the Yangze and the Huang He rivers. It was completed during the Sui dynasty (581-618 CE).

All of these statements about overland trade and transport in the classical era are correct. Overland trade was typically cheaper than oceangoing trade, but it was more dangerous and much more likely to be subject to political disruption. Overland trade was primarily carried out by caravans of pack animals, like horses and camels. Although trade was more difficult in places without a reliable system of roads, it was hardly impossible.