Although the town he is in bears the same name on both sides of the bridge, each side actually has a different nationality. It is the town of El Marco, divided between Spain and Portugal.
While the Spanish part belongs to the municipality of La Codosera in Badajoz, the Portuguese part corresponds to that of Arronches, separated by the narrow channel of the Abrilongo stream, a tributary of the Gévora river which, in turn, is a tributary of the Guadiana, to which it joins near from Badajoz.
From the Spanish side, the place of El Marco is about three kilometers from La Codosera and very close to the sanctuary of Chandavila. The small bridge was built by the residents of the place centuries ago, with a few simple wooden planks, enough to cross the narrow bed of the river, but which were washed away by the waters on days of abundant rain and storms.
Over time it became more stable and elements were added, such as a handrail on one of its sides. But it would not be until 2008 that its remodeling would be undertaken, making it a full-fledged bridge with modern materials and providing the strength that it previously lacked.
The initiative was carried out by the Portuguese city council of Arronches, for which European funds were used. And the works were carried out, as befits an international bridge, by workers from both sides of the border, each starting from their part.
Even in each one of the parts there are some milestones that inform the country in which we are, with an E carved in the Spanish area and a P in the Portuguese area.

It measures 3.20 meters long by 1.45 meters wide, which does not allow the passage of vehicles except motorcycles and bicycles. With that length, it happens to be the shortest international bridge in the world, displacing the one that joins the US island of Zavikon with a smaller one that belongs to Canada in the middle of the Saint Lawrence River, about 4 meters longer.
Sources
History of La Codosera / Ruralea / El Periódico de Extremadura / Do not tell my mother that I am taking photos / Wikipedia.