Subte is Buenos Aires subway lines designated by the letters of the alphabet and a color. Every subway station has an agent to purchase tickets fare is generally ARP0.70, inquire about multi-ride tickets or passes in Spanish. Some stations are very crowded so you may wish to buy more rides to use later to avoid those stations with long lines.
The most distinctive of the lines is the original A line with their old stock cars still running service with its wood interiors, quaint lighting and each door is manually opened and closed by the rider.
Subway schedules vary by the day of week and line, generally Monday-Saturday around 6am or earlier till around 9pm to 11pm, Sunday service starts around 8am till around 9pm to 11pm, depending on the line. You shall need to go on the bus outside the range of the subway schedule, fare ARP0.80 which takes only coins, go by taxi, or walk.