A pontoon bridge is a strange thing to stake a city's identity on. It bobs with the water. It cannot carry heavy traffic. It must open for ships, interrupting every crossing. And yet the Queen Emma Bridge has done all of this across Sint Anna Bay since 1888, connecting the Punda and Otrobanda quarters of Willemstad with a walkway that rides on the surface rather than arching above it. The bridge was named for Emma of Waldeck and Pyrmont, who was queen consort of the Netherlands during its construction -- a German-born princess whose name now belongs to a Caribbean pontoon. The design is mechanical and satisfyingly visible: on the end opposite the hinge, a small shelter houses the operator's cabin where the diesel engines and propellers do their work. Nothing is hidden. You can watch every stage of the bridge opening and closing from either shore.

From 1901 to 1934, the bridge charged a toll -- but with a notable exception. Anyone without shoes could cross for free. On an island where wealth and poverty were written on the body in the most literal ways, the rule was a rare concession: if you could not afford shoes, the colony would not charge you to walk across its bridge. The toll disappeared in 1934, and the bridge has been free to all since. In 1955, lighting arches were installed along its length to celebrate a royal visit by Queen Juliana and Prince Bernhard, giving the bridge its distinctive nighttime silhouette -- a ribbon of light curving across dark water. When the bridge swings open today and the ferries shuttle pedestrians across the gap, those ferries are free of charge too. The tradition of free passage has outlasted the toll by nearly a century.

For its first 86 years, the Queen Emma Bridge carried everything: pedestrians, carts, and eventually automobiles, all bouncing across a pontoon surface that was never designed for the weight of motor traffic. That era ended in 1974, when the Queen Juliana Bridge opened further inland -- a soaring concrete span that arches 56 meters above the bay, high enough for any ship to pass beneath without interrupting traffic above. All motor vehicles were diverted to the new bridge, and the Queen Emma became pedestrian-only. The change suited her. Freed from the weight and noise of cars, the old bridge became what she had always been best at: a place to walk slowly between two worlds. From Punda's side, the view is Otrobanda's broad waterfront and the coral walls of Rif Fort. From Otrobanda, it is the row of narrow merchant houses along Handelskade, their facades painted in the yellows and blues and terracottas that appear on every postcard of Curacao.

The bridge has been completely renovated four times: in 1939, 1961, 1983-1986, and most recently in 2005-2006. Each renovation has preserved the essential mechanism -- the hinge, the propellers, the operator's cabin -- while updating the structure underneath. She is, by Caribbean infrastructure standards, remarkably well maintained. Part of what keeps her relevant is sheer charm. The Queen Juliana Bridge is taller, stronger, and more practical, but no one calls it by a nickname. No one stops to watch it do anything. The Queen Emma Bridge performs for her audience several times a day, swinging open with a mechanical grace that makes tourists reach for their cameras and locals check their watches. After more than 130 years of floating, swinging, and carrying Willemstad across the water, the Swinging Old Lady remains the most photographed structure in Curacao and the emotional bridge between the two halves of a city that has always defined itself by its two sides.