The Inca trail with a bridge and border gate.

The Inca road system was the most extensive and advanced transportation system in pre-Columbian South America. It was at least 40,000 km. long.
The construction of the roads required a large expenditure of time and effort.
The network was composed of formal roads carefully planned, engineered, built, marked and maintained; paved where necessary, with stairways to gain elevation, bridges and accessory constructions such as retaining walls, and water drainage system. It was based on two north–south roads: one along the coast and the second and most important inland and up the mountains, both with numerous branches.
It can be directly compared with the road network built during the Roman Empire. The road system allowed for the transfer of information, goods, soldiers and persons, without the use of wheels. The roads were bordered, at intervals, with buildings to allow the most effective usage: at short distance there were relay stations for chasquis, the running messengers; at a one-day walking interval tambos allowed support to the road users and flocks of llama pack animals. Administrative centers with warehouses, called qullqas, for re-distribution of goods were found along the roads. Towards the boundaries of the Inca Empire and in newly conquered areas pukaras (fortresses) were found.
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