Shinjuku Station is apparently the world's busiest station (though I have never found a reliable source for this assertion). With the JR station (serving four seperate lines including the Yamanote Line), three private railway stations and four underground stations, it is a very complex structure which has grown in a haphazard way over the years.
The photos below give an impression of this growth; they're arial photos taken at five year intervals between 1974 and 1989, with a recent satellite photo for comparision. The aerial photos are taken from the website of the Japanese Ministry of Land, Infrastructure and Transport (国土交通省) and are licensed for general use.
The photos are centred on the station's "South Exit" (南口), which is located on the roadbridge crossing the JR tracks on the station's southern side.