ENGINEERINGThe extraordinary greatness of the Roman Empire manifests itself above all in three things: the aqueducts, the paved roads, and the construction of the drains. -- Dionysius of Halicarnassus, Greek historianThe Romans were extremely innovative builders. The biggest and probably the most important engineering feat the Romans achieved was the construction of aqueducts. These aqueducts were used for two crucial purposes among others, water supply and water flow out. Water for everyday use for private and public washrooms, fountains, etc., was diverted in from nearby rivers and lakes, and the waste water (primarily sewage) from the city was channeled out to far-away water bodies. These aqueducts later formed the technical base for the invention and use of artificial canals and piped-water supply.The Romans brought in the concept of building domes - a spacious and inexpensive alternative to the tedious number of columns needed to support a heavy roof. The Romans also discoveredconcrete - a faster drying and waterproof material than the concrete used earlier. The traditional concrete mix of limestone and sand was mixed with pozzolana (a form of ash-sand material found near volcanoes). This new mix was stronger, more reliable, cemented quickly, and could be molded into any shape required.Another important achievement of the Romans is the construction roads. The Romans built theirhighways using a base of heavy stones and covered it with gravel and/or mud, which helped thedrainage process. At the peak of their reign, the Romans had built over 50,000 miles of highways; some of which are still in use as they were centuries ago. They constructed their highways and roads with the sole purpose of longevity. Modern-day United States has a little under 50,000 miles of highway which are built using a mix of concrete pavement and asphalt, and require regular maintenance and upgrade. The Romans believed in forcing their way through nature, instead of building around it. This led to the 'invention' of digging tunnels for roadways.They brought into practice a universally-defined width for roads. These roads were used for vehicular (carts, carriages, etc.) and pedestrian traffic. In fact, it is often believed that Via Sacra, the main street of ancient Rome, had as much pedestrian, cart and carriage traffic as modern-day Manhattan would, at say, seven in the morning. Most of these roads were paved (main city),some were rubbled (city and suburbs), some were properly lined with sand (generally country side), gravel or mud, while a few others were corduroy roads. Corduroy roads were constructed mostly on swampy and marshy land, with a log of timber and sand covering. Robustly-constructed and well-maintained roads connected all the major cities of the Roman empire to Rome.