Santiago has a great subway system. Very clean, modern, safe. It's better than New York's subway.
It costs around a dollar to get on unless you were just on a bus, in which case it's around 10 cents.
When it's really busy, they have green trains and red ones. Some stations are green, others red. Trains only stop at stations with their color. Stations that are heavily used or where lines cross are both colors. When it's busy, the air in the train gets hot and stuffy, and when you get off, you breathe in the cool, smoggy air with great enjoyment.
I was on a train once where you could not get away with touching less than 8 people. Talk about personal space going to absolute zero. This creates problems when your stop comes along and there are 6 feet of people that are almost incapable of moving in between you and the doors. Trying to grab a handle or something as the train accelerates when it is this full is pointless... everybody is packed in so tight that you can't move in the first place.
When It's not busy, or when you are getting on at one of the terminal stations, you may have a chance of getting a seat. This is a rare privilege.
The lines are mixes of underground, elevated, and ground-level tracks. Visible metro parts are apparently considered an eyesore, because you don't see any of that on the nicer side of town.
Here is a map of the 5 current functional lines. 2 more lines are under construction.
This is the uniquely styled bus terminal cover at the "Del Sol" station.
This is a typical elevated station.
This is the inside of an underground station.
This is the interior of an elevated station.