Basic Information
A viaduct (Latin: "road leader") is essentially a bridge writ large - it is a raised structure designed to convey a road or railroad across a depression (typically a valley, estuary or similar large gap. These are a step up from an embankment in that they have actual bridgework rather than piled earth and thus clearance underneath.
The archetypal viaduct is probably the late nineteenth to early twentieth railway viaduct - typically brick built and composed of a long series of arches - but earlier examples include Roman works where an aqueduct and viaduct are combined, with a road carried on a separate deck from the water. Viaducts are preferred for railway use as trains have a very limited tolerance for gradient and it is often easier to bring the ground to them than have them follow the ground, whereas wheeled vehicles are more tolerant.
Sources
Game and Story Use
- Probably an impressive engineering work in most fantasy settings - most European nations lost the ability to make them in the Classical era and only regained it around the railway era - and may well be greatly wondered at after the end.
- In some locations, especially urban ones, the arches of a viaduct can often be filled in and inhabited (or at least used for commercial or industrial purposes). Rural occupation of viaduct arches appears less common, but should be entirely possible.
- An estuarine viaduct could well have a floating/stilt village attached to its pillars.