The São Francisco Ruins are the remains of an unfinished 19th-century church in Curitiba's historic centre. The stone arches and walls stand just off Largo da Ordem, giving the old quarter one of its most atmospheric fragments of history.
This is a quick stop, not a major monument, but it fits naturally into a walk through the Sunday market, colonial streets, and surrounding museums. The open-air setting also makes it a useful pause when the historic centre is busy: a small place to look at the city's older layers without needing a ticket or a timetable.