Oaxaca’s Day of the Dead just gained a new landmark. In Jalatlaco, a 250-square-meter sand tapestry by local artist Fernando “Beta” transforms a vanished river into a path of color. The piece, titled El río que se hizo camino, is on view in the atrium of San Matías Jalatlaco and will be on view through November 3. It’s art as public memory—quiet, v…