I moved to Buenos Aires (BA) almost exactly 8 years ago. For those who have never been here, let me tell you some things about it. It's large. Do you know Sao Paulo? A bit smaller. Much smaller than Mexico DF. About the same size as New York. Twice the population of the Randstad. About the same as greater Paris or Istanbul. So figuring out a way to move around it was important.
The way most natives do it is by bus. There is a pretty extensive and efficient network of buses which will take you anywhere. There are maybe 150 different lines, but if you don't know the city, specially the place you are trying to reach, they are a recipe for getting lost, because you can (will) miss your stop and end anywhere else.
To make it worse, I get dizzy on buses. The braking and starting makes me really sick. I can control it, as long as I look out the window, or straight forward, and breath really carefully.
So, since I don't drive, and cabs are relatively expensive, I always preferred the subway, or, as it is called here, the subte. Plus, on trains and subways I can even read and not get dizzy. I always tried to live close to a station, I had almost one hour to read while traveling and we got along great.
The subte is pretty old. The first in Latin America, and still the only one in a few million nearby square miles. But it's also ... quirky.
For instance, I lived in Belgrano, close to the D line. Which had japanese cars. How did I know they were japanese cars? Well, they had all these things written on the windows in Japanese. Sadly, I can't find pictures of that, and in a recent trip I didn't see them, so it may be that after maybe 20 years someone decided to rub them off. That's a pity. I always imagined they said interesting stuff, even if they probably said "keep your hands inside the car, you idiot".
There's also the boletería-kiosco. A kiosco is a sort of mini drugstore, where you can buy candy, a soda, maybe a comb, or condoms. A boletería is a palce where you buy tickets to ride the subte. And in some places, you can do both things. Because they turned the ticket booths into kioscos.
Tere is the line at Retiro station, in the C line. There's 4 or 5 boleterías. When you get there, often there's 40 or 50 people in line on the first one. And you can walk just beside them and buy a ticket in the 4th or 5th booth, where there's noone waiting.
And of course, a classic, the one every tourist sees. The A line. The original BA subte, opened 90 years ago or so... and still using the same cars. Yes, you can ride antique, wooden cars to work on that line. With incandescent bulbs on glass tulips. With manual doors (manual opening only, they close automatically with bone crushing force).
Sure, it's hot. There's no air conditioning, and BA can get pretty hot in summer. But it's nice in winter! It's fast, you can't get lost, and it's just so BA.