Café Tortoni Opens on Avenida de Mayo
ESTIMATED75% CONFIDENCEWikipedia[1] gives the year only - "First opened in 1858 by a French immigrant" - with no month or day, so the pin sits on that year's last day.
Café Tortoni first opened in 1858, started by a French immigrant who named it after a Paris cafe, and became the room where Buenos Aires argued about itself - Borges, Gardel and Rubinstein among the regulars whose likenesses now sit at its tables. It still trades on Avenida de Mayo with its original marble, mirrors and tango cellar.