This was the first subway line in Buenos Aires, and it still retains its original cars. The line was opened in 1913, making the Buenos Aires subte the 13th-oldest subway system in the world, the oldest in South America, and the fourth-oldest in the Americas as a whole (after New York, Boston, and Philadelphia). The A line runs under Avenida de Mayo, beginning at Plaza de Mayo, through Congreso, its original terminus, though it now continues much farther. The old cars are wooden and rickety, and as they proceed along the bends underground, you can watch the whole car shimmy and shake. The cars' wooden side panels are made to bend and slip into each other. Windows are still wooden, with leather pulls. Rings, now plastic, are also held by leather straps. Be aware that, unlike those on the cars of the other subway lines, the doors on this line do not always open and close automatically. The system has begun adding new cars to this line, meaning fewer wooden trains are running, but about every third car passing will be one of these historical treasures. It's worth the wait to ride one. Stations between Plaza de Mayo and Congreso still retain most of their early ornamentation as well; the best station is Perú.