Tokyo Station (Tôkyô-eki) is Tokyo's main intercity railway station, although it is not the city's largest (Shinjuku Station), nor is it the busiest (Shinjuku again, with Ikebukuro Station in second place). This is mainly due to the fact that it is only served by a bunch of JR lines and the Tokyo Metro's Marunouchi Line: most of the other subway lines stop at separate stations within a several-block hike of Tokyo Station.
The station is located in Tokyo's Chiyoda Ward, two long blocks east of the gardens of the Imperial Palace, tucked between the old money business districts of Marunouchi to the west and Yaesu to the east. The Marunouchi side, a reconstruction of the station's original 1914 design, houses the commuter lines: the Yamanote Line that loops around Tokyo, the Chuo Line to Shinjuku and 'burbs west, the Keihin-Tohoku Line to Saitama and Kanagawa, and the Tokaido Line which follows the Pacific coast all the way to Osaka.
The newer, bigger, glassier Yaesu side is where the Shinkansen—the high-speed lines plied by what gringos like to call "bullet trains"—terminate. All of the Shinkansen, with the exception of the new and runty Kyushu Shinkansen, ultimately lead to these platforms. The Yaesu side is also where JR's intercity buses stop, and houses a rather large Daimaru department store.
Underground, beneath the Marunouchi side, are the platforms for the Yokosuka Line and Sobu Line, which go to Kanagawa and Chiba respectively (the latter is also the line that takes you to Narita Airport), as well as the Marunouchi Line station that feeds into the ridiculously complicated Tokyo Metro network. A good 200 meters south, buried several stories underneath the Tokyo International Forum, is the platform for the Keiyo Line to central Chiba, which is the line you'll take if you're going to the Tokyo Disney Resort.
Despite being only second-biggest in Tokyo, Tokyo Station is still huge. The ten above-ground platforms fill a breadth of about 250m, and the longest Shinkansen platforms are 500m long. Counting the underground passages that link the station to surrounding office buildings and subway stations, Tokyo Station stretches out over the better part of a square kilometer. It's big, it's crowded, and it will get you just about anywhere you want to go.
Limited express trains from Tokyo Station
Map
Somewhat oddly, there are a few series of platform numbers in Tokyo Station. The regional train platforms are numbered 1 through 10, the Shinkansen platforms are 14 through 23, and there are also two sets of four platforms underground, each of which is independently numbered 1 through 4. So there are actually three very different "platform 3"s at the station. See the rough diagram below:
Y A E S U S I D E
^^^^
----19--Tokaido/Sanyo Shinkansen--------------------> ||||
----18--Tokaido/Sanyo Shinkansen--------------------> ||||
----17--Tokaido/Sanyo Shinkansen--------------------> ||||
----16--Tokaido/Sanyo Shinkansen--------------------> ||||
----15--Tokaido/Sanyo Shinkansen--------------------> ||||
----14--Tokaido/Sanyo Shinkansen--------------------> ||||
<---23--Tohoku/Joetsu/Nagano Shinkansen-------------- ||||
<---22--Tohoku/Joetsu/Nagano Shinkansen-------------- ||||
<---21--Tohoku/Joetsu/Nagano Shinkansen-------------- ||||
<---20--Tohoku/Joetsu/Nagano Shinkansen-------------- ||||
(interchange gates) ||||
----10--Tokaido Main Line---------------------------> Keiyo
-----9--Tokaido Main Line---------------------------> Line
-----8--Tokaido Main Line---------------------------> ||||
-----7--Tokaido Main Line---------------------------> (under
-----6--Keihin Tohoku Line--------------------------> ground)
-----5--Yamanote Line-------------------------------> ||||
<----4--Yamanote Line-------------------------------- ||||
<----3--Keihin Tohoku Line--------------------------- ||||
-----2--Chuo Line-----------------------------------> ||||
<----1--Chuo Line------------------------------------ ||||
(underground) ||||
-----1--Yokosuka Line-------------------------------> ||||
-----2--Yokosuka Line-------------------------------> ||||
<----3--Sobu Rapid Line/Narita Express--------------- ||||
<----4--Sobu Rapid Line/Narita Express--------------- 1234
M A R U N O U C H I S I D E
Future plans
If you visit Tokyo Station today (2006), you'll notice that much of it is under construction. JR is extensively renovating the station, by restoring the Marunouchi side to its historical glory and by rebuilding the Yaesu side with a new entryway and twin towers at either end to house office and shopping space.