Subway station having a place to pray to or thank God for safe travels, comforting and artistic or a pretty bad sign?
Like all subways, the interior of the stations and the cars themselves are plastered with advertisements. In the subway you can find out about events, concerts, services, schools and more. Anything big is bound to be advertised there. The main postings are of course punctuated with the unauthorized postings offering services from courier to prostitution, and everything in between.
The Subte also often functions as a center of commerce. There are the institutionalized - ticket sales, in station kiosks and newsstands. However, there are also people selling goods off towels and blankets laid along the halls. They are usually in the same place everyday, so they're almost de facto institutionalized. In my station it's bootleg Nike and Adidas socks; the same salesperson isn't always there, but the same "store" is. The next tier down is the traveling sales men. These people not only troll the stations, usually offering 1 product for sale (gum, tissues, scissors), but actually get on and off the subway to sell in transit. In the cars their sales methods are particularly aggressive, and consist of going to every subway rider and handing to or laying on their leg whatever product is for sale (you know? to give you some time to check out the product or think over a purchase). Then they make a second rotation collecting payment or the items back. Sometimes the product sold in the subway car is nothing more than a trading card with a poem or religious picture. In these cases, when the product isn't something anyone will actually want, the seller is usually a child under 10 years old essentially trying to capitalize on sympathy. This leads me to the lowest level of commerce which are people asking for money. Though don't be fooled, not all of them are beggars. Some people perform for money. You can find all types of musicians, performing all types of music on all types of instruments. Like the de facto store owners, some of these people have a routine and location, but others travel. Just yesterday (or maybe the day before) there was a violinist performing on my crowded rush hour ride. A variation on this is a blind man in my station, who dresses everyday in a 3 piece suit to play music from a stereo that sits on his lap. Lastly, of course, there are plain old beggars. People sitting, if they're crafty enough with their baby, asking (either with words or the universal sign of a cup with a few coins) for money.
Not all of the secondary functions of the Subte are bad. For example, the music is great if you don't have an iPod, or just want to be exposed to a different type of music. The art can also be interesting. As I said in my street art post, subway cars are sometimes colorfully spray painted, which can really break up the monotony (albeit make it impossible to see if the car is full or empty, or if people are trying to get off). Because the stations are pretty heavily policed, graffiti in the stations is generally limited to short written messages. The other morning however, I noticed a new one in my station, which I am delighted to pass every morning. (Bonus! It's in English...err kinda, minus the word order issue.)