7) Roads
The longest trackway was the Diolkos near Corinth, Greece, measuring between 6 and 8.5 km. The paved roadway allowed boats to be pulled across the Isthmus of Corinth, thus avoiding the long and dangerous sea trip around the Peloponnese peninsula. Working by the railway principle, with a gauge of around 160 cm between two parallel grooves cut into the limestone paving, it remained in regular and frequent service for at least 650 years. By comparison, the world's first overland wagonway, the Wollaton Wagonway of 1604, ran for 3 km.
8) Roofs
The largest prop-and-lintel roof by span spanned the Parthenon in Athens. It measured 19.20 m between the cella walls, with an unsupported span of 11.05 m between the interior colonnades. Sicilian temples of the time featured slightly larger cross sections, but these may have been covered by truss roofs instead.
The largest truss roof by span covered the Aula Regia (throne room) built for emperor Domitian (81–96 AD) on the Palatine Hill, Rome. The timber truss roof had a width of 31.67 m, slightly surpassing the postulated limit of 30 m for Roman roof constructions. Tie-beam trusses allowed for much larger spans than the older prop-and-lintel system and even concrete vaulting: Nine out of the ten largest rectangular spaces in Roman architecture were bridged this way, the only exception being the groin vaulted Basilica of Maxentius.
9) Tunnels
The deepest tunnel was the Claudius Tunnel, constructed in eleven years time by emperor Claudius (41–54 AD). Draining the Fucine Lake, the largest Italian inland water, 100 km east of Rome, it is widely deemed as the most ambitious Roman tunnel project as it stretched ancient technology to its limits. The 5653 m long tunnel, passing under Monte Salviano, features vertical shafts up to 122 m depth; even longer ones were run obliquely through the rock. After repairs under Trajan and Hadrian, the Claudius tunnel remained in use until the end of antiquity. Various attempts at restoration succeeded only in the late 19th century.
The longest road tunnel was the Cocceius Tunnel near Naples, Italy, which connected Cumae with the base of the Roman fleet, Portus Julius. The 1000 m long tunnel was part of an extensive underground network which facilitated troop movements between the various Roman facilities in the volcanic area. Built by the architect Cocceius Auctus, it featured paved access roads and well-built mouthes. Other road tunnels include the Crypta Neapolitana to Pozzuoli (750 m long, 3–4 m wide and 3–5 m high), and the similarly sized Grotta di Seiano.
The longest tunnel as well was the 94 km long Gadara Aqueduct in northern Jordan. This recently discovered structure provided for hundreds of years water for Adraa, Abila and Gadara, three cities of the ancient Decapolis. Only 35 km long as the crow flies, its length was almost tripled by following closely the contours of the local topography, avoiding valleys and mountain ridges alike. The monumental work seemed to be carried out in seven stages of construction between 130 and 193 AD. The distance between the individual vertical shafts was on average 50 m. Probably the project was initiated by Hadrian, who had granted privileges to the cities during a longer stay in the Decapolis. The aqueduct remained operational until the Byzantines lost control of the region after the Battle of Yarmuk in 636.
The longest tunnel excavated from opposite ends was built around the end of the 6th century BC for draining and regulating Lake Nemi, Italy. Measuring 1600 m, it was almost 600 m longer than the slightly older Tunnel of Eupalinos on the isle of Samos, the first tunnel in history to be excavated from two ends with a methodical approach. The Albano Tunnel, also in central Italy, reaches a length of 1400 m. It was excavated no later than 397 BC and is still in service. Determining the tunnelling direction underground and coordinating the advance of the separate work parties made meticulous surveying and execution on the part of the ancient engineers necessary.
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