The park has a birthday, which is rare for a place born out of empty boulevards. In 1900 the provincial government let the city expropriate four public squares where two new avenues crossed, and Rosario hired Carlos Thays to design something grander. Thays was the landscape architect behind the Buenos Aires Botanical Garden, and he gave Rosario an artificial lake, internal avenues, and - using the earth dug out for the lake - a small artificial hill that locals still call La Montañita, the Little Mountain. During the city's first Festival of the Tree, schoolchildren planted six thousand trees here. The park opened on the first day of 1902. Many of those saplings are now the canopy you walk beneath.

Thays understood that a park is a sequence of rooms, each with its own mood. The Rosedal, the rose garden, was finished in 1915 and filled with sculpture, fountains, and dozens of varieties of roses. The French Garden arrived in 1942, formal and symmetrical, anchored by a large marble fountain. There is a children's garden built around play and learning, and across the grounds three museums collect the city's memory: the Museum of the City, opened in 1902 in what was once a school for apprentice gardeners; the Juan B. Castagnino Fine Arts Museum, opened in 1937; and the Dr. Julio Marc Provincial Historical Museum, opened in 1939. A single afternoon here can move from roses to Renaissance painting to the long story of Santa Fe.

This was never only a place of quiet. The Jorge Newbery Municipal Stadium, begun in 1925, was the first state-funded sports venue built for public use anywhere in Argentina - a small revolution in a country where clubs were usually private. The park hosts three of them still, including Newell's Old Boys, one of Rosario's two great football institutions and the club whose youth academy once shaped a left-footed six-year-old named Lionel Messi. There is a municipal skating rink that has drawn world championships, fairgrounds first meant for agricultural shows, and the old racetrack of the Rosario Jockey Club. Sport and leisure were written into the park's purpose from the start.

Rosarians sometimes call their parks the lungs of the city, and this is the oldest and largest of them. On a warm Sunday the lawns fill with families sharing mate, the bitter green tea passed hand to hand, while runners loop the lake and couples drift through the rose garden. The calendar of flowers still gets rewritten at dusk; the racetrack of the old Jockey Club still draws a crowd; the museums open their doors to schoolchildren whose great-grandparents may have planted the trees outside. Carlos Thays designed for crowds like these - not a museum to be admired from a path, but a working public space, generous and a little wild at the edges. More than a century after those schoolchildren bent over their six thousand saplings, the trees they planted are doing exactly what was asked of them: throwing shade over a city that needs it. A park, in Rosario, is not scenery. It is infrastructure for daily life, and this one has been carrying that weight for over 120 years.