Viaduc d'Austerlitz

The Viaduc d Austerlitz is a feat of engineering that forces the Seine to accommodate its architecture rather than the other way around. Built between 1903 and 1904 to carry Paris Metro Line 5 across the river, its builders could not place any pillars in the water because they would have disrupted the constant flow of river traffic. To solve this, they created a single massive span of 140 meters held up by two grand parabolic steel arches, an audacious design choice that keeps the riverbed entirely unobstructed.