Heptastadion
About
A roughly seven-stadia (c. 1,300m) mole/causeway built under Ptolemy I connecting the mainland to Pharos island, dividing Alexandria's harbor into the Great Harbor and the harbor of Eunostos. Functioned as both a dam and a road; still in use in 117 CE. Later silted up and built over, forming the base of the modern city's Ras el-Tin peninsula neighborhood, so its exact ancient course is only approximately reconstructable -- point marks the traditional midpoint. Used 'road' as the closest existing category rather than adding a new one for a single feature.
What happened here
The surface is cambered, drained on both sides, and built to be repaired rather than to last forever. Milestones give the distance to the nearest town and the name of the emperor who last paid for resurfacing. Traffic is mostly feet and hooves; wheeled freight is slow and heavy and, in some towns, banned during daylight. Official messengers use the state relay and change horses at posting stations set roughly a day apart, which is what makes the empire governable. Everyone else walks about twenty miles a day and stops at an inn of doubtful quality. Tombs, shrines and roadside bars line the approaches to any town. Bandits are a real risk on quiet stretches and the army patrols the worst of them.
Sources
Roman Maps shows the empire frozen at 11 August 117 CE, the day Trajan died — its moment of greatest territorial extent. Explore the full map →