Confitería Ideal is a historic cafe in Buenos Aires, while others flock to Cafe Tortoni, I recommend running (not walking) to La Ideal.
Open since 1912, it closed in 2017 for repairs and to be remodeled. It reopened in 2022, bright and shiny in full Bell Epoque splendor. The quality of their coffee and food shines above the competition so while it is admittedly pricey, I do think it is worth it for the food and the space itself.
La Ideal used to be one of the city's most beautiful Milongas (tango dance halls) but unfortunately the milongas did not return in the 2022 re-opening.