Chimarrão is not a tourist attraction but it is one of the defining experiences of time spent in Porto Alegre, and understanding it makes everything else make more sense. The drink is maté — the dried and ground leaves of the yerba mate plant — prepared in a distinctive way: packed into a cuia (a gourd, traditionally made from an actual gourd but now often wooden or leather-covered), moistened with hot (not boiling) water, and sipped through a bombilla (a metal straw with a filter at the bottom). It is intensely bitter, an acquired taste, and consumed in enormous quantities throughout the day.
The social ritual is what matters. Chimarrão is shared: the cuia is passed from person to person in a circle, each person drinking it dry before passing it on. Accepting the gourd when offered is a gesture of welcome; refusing is mildly rude. You will see people carrying their own thermoses and cuias absolutely everywhere: on public transport, in parks, at bus stops, at work, at football games. The Brique da Redenção on Sunday morning is one long chimarrão circle. The best place to buy your own equipment — and you should buy your own — is the Mercado Público, where stalls sell quality cuias in silver, wood, and gourd forms alongside bombillas ranging from simple to elaborately engraved. This is the ideal souvenir from Porto Alegre.