One popular day trip from Buenos Aires involves taking a ferry over the (very wide) river to Colonia, in Uruguay. You can visit the UNESCO Historic Quarter…
… have lunch at one of the many outdoor eateries, enjoy the fresher air …
… and take the ferry back as the sun is setting.
Just be sure not to miss the large map after you get out of the ferry terminal.
My cousin did, and she spent most of the day in the non-heritage part of Colonia, photographing ants.
