The ground Caminito stands on has changed its mind about what it is several times over. In the 1800s a small stream ran here, draining into the dark Riachuelo at the bottom of the barrio, crossed by a little bridge the Genoese immigrants of La Boca called the Puntin. When the stream dried up, railway tracks for the old Ensenada port line were laid along its bed, and you can still find the disused rails today at the alley's end, on Garibaldi Street. Then in 1954 the railway closed too, and the abandoned corridor became a landfill, the eyesore of the neighborhood, a place people threw things away rather than a place anyone walked.

Benito Quinquela Martín had every reason to look away from that ruined lane, and instead he transformed it. Abandoned at a foundling home as an infant in 1890 and raised by a coal-yard family in La Boca, he had grown up hauling sacks at the very port whose grit he would spend his life painting, slim enough as a boy that the dockworkers nicknamed him "Mosquito." He became Argentina's great painter of the harbor, laying oil onto huge canvases with a spatula until the ships and smoke stood up off the surface. Over three years in the late 1950s he prepared the walls along the dead railway street and washed them in pastel colors, the same palette that filled his paintings, and the dump began to glow.

The name was already famous before the place was. "Caminito" is one of the most beloved tangos ever written, composed in 1926 by Juan de Dios Filiberto, a friend of Quinquela Martín and, like him, a son of La Boca. The song is a lament for a little path where a lost love once walked, and when the painter restored this particular alley he borrowed its name, fusing melody and masonry. By 1960 he had set a stage at the southern end, and the street became an open-air museum, the rare kind you do not enter so much as wander into, where the art is the buildings and the music is in the air.

Today Caminito is unapologetically a show, and that is part of its honesty. Couples dance tango for the tourists; vendors sell paintings of the very tenements you are standing among; cutout figures of Diego Maradona and Carlos Gardel lean from upper balconies. Purists sometimes sniff at the spectacle, but the spectacle is the point and always was: a poor immigrant barrio that decided its own beauty was worth celebrating, loudly, in primary colors. The corrugated-metal houses of La Boca were once painted with whatever leftover marine paint the dockworkers could scrounge, a different color for every wall. Quinquela Martín simply gave that scrappy instinct a stage, and named it after a song about not forgetting.