The New York Subway system is the world's largest subway systems that serves four of the five boroughs of New York City, New York: the Bronx, Brooklyn, Manhattan, and Queens..  It is comprised of some 468 stations and covers a distance of over 200 miles.

Over 5 million passengers use the system daily, making it the busiest rapid transit system in the United States and the seventh busiest in the world.

There are 27 different routes in NYC subway network.  Some routes are assigned a number while others are known by a letter. You can find transit maps online here.

You go down these stairs to the subway platform.
 
You will pass through subway turnstyles to reach the platforms.
Here is information about transit fares and tolls in New York.
To enter the subway, slide a MetroCard in a turnstile. The turnstile will admit you once the fare has been paid. The train line you want should be clearly marked. Trains largely run uptown or downtown. Make sure you are going in the right direction.
 
Get on the train. Subway platforms will typically have several subway lines traveling though a single station. Be careful to board the proper train. When the train arrives, allow passengers to exit before you board. You can sit or stand. If standing, keep your balance by holding on to a railing.
Get off at your destination. You can generally find the route each subway line takes by looking at your personal map or the map in every subway car. As the train pulls into each station, its arrival will be announced over the speakers in each car. Some subway lines have an electronic billboard in each car that shows passengers the route as well as which subway station is next.

While visiting New York City for the first time, you will probably use the subway. If you are not careful, you might never get to your destination. The subway in New York City is one of the largest subway systems in the world in terms of track mileage and number of stops (472), and one of the only 24 hour subway systems in the world.

Make sure you have a map of the subway system. You can ask for a free map from the nearest subway clerk. Maps are printed in every station and inside all subway cars. Subways travel by predetermined routes. The routes and the stations along the routes are printed in different colors on the maps. Subway routes are either lettered or numbered, and the letter or number is printed on the subway car and platform.

Buy a MetroCard. New York City subways no longer take tokens. All fares are paid by MetroCards — thin, electronic pieces of rectangular plastic with a magnetic strip at one end. Cards can be purchased from a clerk at a station or from a machine. A MetroCard can be purchased for a single ride or multiple rides. Fares are reduced if multiple rides are purchased. Riders can also buy MetroCards that allow them to travel the subway for a day, week or month.

In addition to the current sophistication of the subway system, most people are not aware that the city has many abandoned and hidden subway stations. Beneath City Hall is one of the hidden subway stations. It has been inactive since 1946. Despite being abandoned, the station is an architectural wonder. It boasts high ceilings, skylights, and antique tiling.

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