VALPARAÍSO, Chile — This glorious yet dysfunctional port has always harbored a darker alter ego, a streetwise subculture founded on poverty. Its credo, spat between gritted teeth, head cocked in vague menace, sends shivers down the spine of any well-to-do Chilean. “Soy un chorro porteño — I’m a punk from the docks.”

Just yards from the city’s quaint cobbled districts, whose artsy residents live amid shingle-walled antiques stores and quirky mansions painted in fanciful shades of indigo and mango, the downtrodden of Valparaíso inhabit a world of urban blight and decay.