Ancient Sumerian war chariots, painting on the Standard of Ur, ca. 2600-2400 BCE

Paths treaded out by animals, which at the same time facilitated the movement of Palaeolithic nomads, can be considered to have been the ancient origins of roads. The routes bypassed natural obstacles or led through rivers or marshland in places where it was relatively easy and safe to cross them.
Humans started marking out routes after the Neolithic revolution, when they took up farming and were thus forced to settle down. The first roads were paved with stone slabs laid on a base made of mud-brick, sand and natural bitumen. The earliest such pathways come from Sumer (present day Iraq). Soon, they also became common in Egypt, where from the beginning of the third millennium BCE ritual roads paved with limestone slabs connected grave complexes at the pyramids to the holy river. They were the routes for ceremonies and processions.
Around 1200 BCE, the Hittites started constructing roads which were partly hardened. The hardened parts were wheel tracks approx. 10 cm deep and approx. 20 cm wide spaced at approx. 1.5 m. Passing loops were not very common so if two chariots were riding from the opposite directions on such a road, one of them had to give way to the other. Someone had to retreat to the nearest passing loop or pull aside. Such pathways were in operation in Greece, southern Italy and Malta, as well as other places.
At larger distances natural routes were used for transportation using pack animals: donkeys, oxen and camels, so there was no option of wide-scale trading. An extensive system of roads was built in the first millennium BCE in connection with the needs of the expansion of empires. Those were mostly natural pathways, paved only in the area of large cities, on intense traffic sections. Their main function was not transportation but a royal postal service. According to records, in Persia message carriers would ride 160 km a day in a relay race system.
Romans were the first great constructors of real roads. Their predecessors usually achieved their objectives through the slight modification of nature. The routing of roads normally matched the relief of the land. Romans marked out their roads straight, disregarding any obstacles. In valleys, they routed roads on embankments to make them overlook the surroundings. In folded areas, they would cut out passages and thus pioneered the construction of tunnels. Roman pathways were extremely robust. They consisted of a few layers of stones of various sizes, joined by lime mortar, concrete or lead. They were approximately one metre thick.

Via Appia called ‘regina viarum’ – the queen of roads – by Romans
An ancient road with stone wheel-ruts in Midas City, Turkey.

Romans did not make provisions for intense wheeled traffic which was only local. This was testified at least by the ‘angular’ shape of the surface of Roman bridges. Goods were transported over long distances almost exclusively by waterways. Quoting an ancient saying “all roads lead to Rome”, because the milestones of any road built by Romans showed the distance to the capital. The network of roads was like a blood circulation system for the huge country ensuring its correct functioning. Messengers travelled to and fro and, if required, it was used for efficient transportation of valorous legions. It was important that the routes were straight to reduce the travelling distance and time. It is estimated that the network of main ‘brick’ Roman roads was approximately 80 thousand km long, and including less hardened ‘second class’ pathways it totalled more than 300 thousand km.
Building such an impressive system of roads, Romans also erected many bridges, viaducts and tunnels (previously, the only bridge crossing a large river was
the stone pillar-based bridge on the Euphrates in Babylon). The first such structures were wooden due to the ease of processing,
good availability of materials and fast rate of construction. In addition, Romans widely propagated the construction with stone arch structures, which made them the world pioneers in bridge construction.
The first (historically documented in the writings of Livius) Roman bridge on the Tiber – Pons Sublicius – was erected under royal rule exclusively from wood using no nails. On the other hand, the Greek historian Herodotus recounted the construction of three important military bridges – two floating structures: across the Danube and the Bosphorus and the third one across the Hellespont (the Dardanelles).
The oldest preserved bridge in Rome is the  double-span structure built in 62 BCE by Lucius Fabricius. In the 14th century the bridge was renovated and topped with two four-headed herms representing Janus, so it is sometimes referred to as the ‘Bridge of the Four Heads’.
A strikingly monumental  structure is Pont du Gard located near Nîmes which has survived to the present almost intact. The three-level, arched stonework was erected without the use of mortar, using only properly prepared stones that adjoined one another closely. This 270 m long and 49 m high Roman work built in the 1st century CE was only a fragment of a 48-kilometre-long aqueduct supplying water to the inhabitants of Nîmes.

A road in ancient Pompeii.
An ancient route in Lebanon – 1st century BCE.

Another example of bridge construction art is the Aelian Bridge in Rome. The five-span structure, built to the order of Emperor Hadrian in 134 CE, connected the then city centre to the mausoleum on the left bank of the river. In the 7th century Pope Gregory I renamed it Ponte Sant’Angelo and the mausoleum was named Castle Sant’Angelo to commemorate a legendary appearance of an angel on its roof who announced the end of the plague. The bridge has an 18 m span and it is 153 m long. Its railings are ornamented with the sculptures of angels erected there to the order of Clement IX in 1668.