A viaduct is a long bridge that carries a road or railway over a valley, river, or other obstacles. It typically consists of a series of arches or spans supported by columns or piers. Viaducts are designed to provide a smooth and safe passage for vehicles and trains, allowing them to cross difficult terrain without interruption. These structures are often made from materials like concrete, steel, or stone, and can vary in design and length. Famous examples include the Millau Viaduct in France and the Royal Albert Bridge in the UK, showcasing engineering advancements and aesthetic appeal.