Engineers Jean Résal and Amédée Alby, in charge of designing the future Alexandre-III bridge, had to follow a precise set of specifications. The bridge had to be flat enough to see the entire Invalides from the Champs-Elysées, but without obstructing the movement of barges. It also had to be symmetrical and decorative. Finally, the width of the bridge had to be proportionate to that of the avenue it would extend. The result was a single-arch metal bridge, 40 metres wide, with massive abutments to resist the enormous horizontal thrust. More than a century after its inauguration, the Alexandre-III bridge is still the most beautiful in Paris.