A viaduct is an engineering work that spans an entire valley, a differentiating characteristic of bridges. The term viaduct comes from the Latin via, path and ductus, which means conduction. However, apparently in Ancient Rome this term was never used, being rather a modern derivation considering the analogy with the word aqueduct. Like Roman aqueducts, many viaducts originally consisted of a series of arches of approximately equal length.

According to the Dictionary of the Spanish Language of the Royal Spanish Academy, a viaduct is a work like a bridge, for the passage of a road over a ravine. In Romance languages, the word viaduct generally refers to a bridge that crosses only land. When the objective of the construction is to cross water, terms derived from the Latin pontem are used, which in Spanish is simply bridge. Although it is possible to consider viaducts as roads (in the case of automobiles) or railway lines (in the case of railways) elevated to cross a valley, whether a valley or a ravine, the term has currently been used in some Spanish-speaking countries to designate other types of bridges that cross either land, water or both. In some Latin American countries, the term is used to designate important avenues, even at surface level "Viaduct (avenue)").

The longest viaduct in antiquity was probably the Pont Serme") in southern France.[1] Viaducts were initially used in countries where railways played an important transportation role as part of the infrastructure for crossing rugged terrain. The low-incline requirement for railway tracks forced the construction of bridges to join two points that were at similar levels, but separated by a ravine or valley. Given the physical properties of the materials originally used, these Bridges had to be built by joining a series of arches, which resembled Roman aqueducts, but over which a railway line passed. Examples are the Filisur"), Solis"), Landwasser") and Lorraine") viaducts, all of them in Switzerland.

With the growth and development of cities and later with the arrival of automobiles, the need also arose to create roads that would allow the passage of land vehicles, mainly in cities located in mountainous areas. Thus, viaducts were built in cities such as Madrid (the Segovia Viaduct) and Luxembourg (Passarelle (Luxemburg)&action=edit&redlink=1 "Passarelle (Luxemburg) (not yet written)").

In large cities, viaducts have proven to be very useful, allowing traffic to travel at higher speeds and drastically reducing transportation times and costs. A large number of viaducts have been built around the world. Many cities have adapted this type of structure to their realities; For example, the Santiago Metro in Chile is used in this way in certain sections (mainly in the middle of wide avenues or places that are difficult to build underground due to flooding).