You'd never know it by looking at the city these days but tramways were once the most important form of transportation in Buenos Aires. If you pay attention you’ll see the rails still buried among the cobblestone all over the city.
After 100 years in operation, the trams disappeared in 1963. But thanks to the Asociación Amigos del Tranvía you can go for a 20 minute ride in the historic trams through Caballito.
The tram ride is free to ride on the weekends on Saturday and Sunday afternoons from 4-7 pm and Sunday mornings from 10 am to 1 pm. You can’t reserve and have to wait in line on a first come first serve basis (so it’s in your best interest to arrive early).
I recommend always checking Instagram pages for these sorts of activities in Argentina in case of special hours or cancellations (like for poor weather).