Given the large overlap between the Hellenistic and Roman civilizations, it is sometimes hard to disentangle which civilization took some technological steps. In a sense it doe not matter, as Rome rose to power within a Hellenistic context, and carried forward the Hellenistic culture a further few centuries.
Some of the greatest technological achievements of the Roman period were in construction engineering. These rested on the development of the first form of concrete in history, a step that took place in southern Italy in the 2nd century BC. This material (which used volcanic lava as its base) was crucial to Roman architectural innovations such as the arch and the dome. These allowed Roman engineers to span much larger spaces than ever before. Huge stone bridges, the first of their kind, were thrown across rivers; multistoried aqueducts marched across valleys; and awe-inspiring buildings such as the Pantheon in Rome, and much later the Cathedral of S. Sophia in Constantinople, used domed roofs to enclose larger areas than any other building until the 16th century.
The Romans were clearly adventurous and highly skilled engineers. More than anything else, this is seen in their roads, which ran for hundreds of miles across all sorts of terrain, and played an important part in knitting the empire together so effectively. Laying out these roads involved advanced surveying techniques, using instruments which were adapted from those used by astronomers to measure angles.
The Romans seem to have been the first to use mechanical means for the ubiquitous task of grinding corn, which previously, had always been done by hand. Dating from the second century BC, heavy millstones have been found which would have ground grain with the aid of animal power.
The Roman world saw the next major step along this path with the building of the first water mills recorded by history. These were used from the first century BC to grind grain, and were described by Roman writers such as Vitruvius and Pliny the Elder. They probably originated in the Greek-speaking eastern empire, but in the first century AD, one mill, in southern France, had no less than sixteen overshot water wheels, fed by the main aqueduct to Arles. It has been estimated that this mill could supply enough bread for the entire 12,500-strong population of Arles at that time.
Some later mills were built as sawmills, for the industrial-scale cutting of timber.There is also evidence for a kind of mechanical harvester or reaper at work in Roman Gaul.