Successful Rome's engineering and infrastructure

[eurofed]

The topic at hand is to review and discuss what kind of engineering endeavors and infrastructure efforts a completely successful Roman Empire would pursue during its history all the way to the Information Age, most definitely including the macro- and mega-engineering kind. This scenario assumes a very successful Roman civilization that keeps its genius and enthusiasm for engineering throughout its history, engaging in several impressive projects at the best of its considerable talents and resources.

Feasible ideas I can think of for the pre-modern period include:
* The Roman road network gets extended across all of Europe, North Africa, and the Near East.
* The Romans build a semaphore telegraph network to improve speed of communications through the empire.
* They establish and maintain the Suez Canal to greatly improve their control of the trade network between India and the Mediterranean. IOTL, a version of the Suez Canal (the Canal of the Pharaohs) intermittently operated from the Pharaohs’ times to the Byzantine period, so the Romans expand on that, eventually creating a replica of the modern project.
* They gradually build a network of canals across Europe that links the major rivers of the continent from Gallia to Sarmatia and the Mediterranean with the North Sea. It allows them to navigate with ease from one end of the continent to the other, for trade and military purposes. A limited version of this was proposed IOTL but the plan was dropped for political intrigues.
* They dig a version of the Kiel Canal - IOTL, a version of this existed since the Middle Ages – which gradually becomes an equivalent of the modern project. They also build an early version of the Corinth Canal. IOTL it was attempted in Nero’s time, and dropped because of his death.
* The qanat system gets gradually spread throughout all the arid regions of the Roman Empire.
* The Romans build the ‘Great Limes’, an extensive set of fortifications on the Vistula-Dniester line to protect the eastern border from the steppe nomads, which becomes the Western equivalent of the Great Wall. It eventually gets abandoned once Rome starts to colonize Sarmatia in earnest, but equivalents are established further east during colonization of the steppes, eventually finding the final version on the Volga or the Urals.

I’m not sure if it would require modern technology or not, but a canal to bypass the Nile cataracts is certainly a possibility. It seems a version of this was built in the Pharaohs’ period for the First Cataract, although like the Canal of the Pharaohs but to an higher degree it required some serious periodic maintenance because of the silting problem.

Feasible projects I can think of that require modern technology include:
* Pretty much any big hydraulic project that was built IOTL in western Eurasia or the Americas, most definitely including the Aswan Dam, the Panama Canal, and the Nicaragua Canal.
* An extensive desalinization and irrigation system in the arid regions of the empire with access to the sea.
* Realization of the ‘Sahara Sea’ project to flood the endorheic basins in the Sahara Desert with waters from the Atlantic Ocean or Mediterranean Sea. This creates a series of inland salt lakes that cover the substantial areas of the Sahara Desert which lie below sea level, bringing humid air, rain and agriculture deep into the desert, and allowing generation of hydroelectricity from the continuously flowing water.
* Thorough exploitation of pretty much any potential hydroelectric source in the empire’s territory, as well as extensive use of nuclear, solar, and wind power.
* An extremely developed railroad, highway, and airport network, with generous use of mag-lev technology.
* Space colonization.

For reference, let’s assume ITTL the Roman Empire avoids, corrects, or overcomes all the causes of its OTL downfall and keeps expanding and absorbing new peoples, territories, and resources to the best of its remarkable abilities. In due time it industrializes much like OTL Europe - probably several centuries earlier b/c of the lack of Dark Ages collapse. During its Classical and Late Antiquity period it holds on to all OTL territories and conquers Germania Magna up to the Vistula-Tyras line, Kush, South Arabia, Mesopotamia, Greater Armenia, western Persia, Caledonia, and Hibernia. Subsequently it assimilates Sarmatia, Aksum, Scandia, and the rest of Arabia and Persia during the Middle Ages. Once it masters Renaissance technology, it colonizes the Americas at least up to the Continental Divide. Quite possibly it may colonize East Africa and Southern Africa as well, although it tends to leave the rest of Africa alone for climate and disease reasons.

Much like OTL China but on a larger scale, TTL Rome grows into a very successful imperial civilization with a civic-universalist perspective and an unbreakable national identity and cultural-political unity, despite occasional periods of strife and disunion. ITTL the Western Eurasian core of the Roman civilization and the very notion of ‘Europe’ grow to include all of OTL Europe, North Africa, and the Middle East. Religions that might become a serious cause of political strife and disunion for Rome, including Christianity, Judaism, and Zoroastrianism, get suppressed, marginalized, or expelled beyond Roman borders, or are simply erased out of existence in Islam’s case. Perhaps Buddhism becomes dominant in the Roman Empire, or maybe European polytheism and Roman philosophy merge and evolve into an sophisticated analogue of Hinduism that becomes the national faith of Rome, or the empire remains quite religiously diverse up to modern times.

As a rule, Rome regards ethnic differences as meaningless and remains tolerant of cultural diversity that does not threaten its political stability, typically being eager and efficient at assimilating and adapting useful or interesting ideas from any source. Nonetheless it is quite ruthless and efficient at suppressing resistance to its rule and potential sources of disloyalty. Imperial unity naturally leads to a high degree of cultural-linguistic cohesion. A fusion of Latin and Greek with serious borrowings from many sources evolves into Rome’s lingua franca that is fluently spoken by the overwhelming majority of Roman citizens. It remains intelligible across the Roman Empire despite some inevitable regional drift.

Steady cultural and trade exchanges between Rome, China, and India since Classical times foster parallel progress in all three civilizations, drive China to avoid the trap of isolationist complacence and high-equilibrium stagnation, and prod India into a path to imperial unity. Over time, the three Eurasian empires grow into the world’s three industrialized superpowers. Most other polities get absorbed or utterly dominated by them, or at the least live in their shadow. Much like Rome in its own turf, China and India eventually go on an expansion and colonization spree of their own, so they absorb most of East Asia, South Asia, Southeast Asia, Oceania, and the western portion of the Americas between them.