On this page there are some maps of London tube system, which is like the subway but in London they call it the London Underground or Tube. The Tube system`s lines stretch for 402 km (that is, 250 miles), making it the third longest metro system on Earth, after Seoul, Korea and Shanghai, China. It has 270 stations stretching all across Greater London, with a handful of stations situated outside the metropolitan area.
The London Tube grew out of the Metropolitan Railway, which was the first underground railway system in the world. That railway now forms parts of the Hammersmith and City Line, the Circle Line, and the Metropolitan Line.
The busiest station in the Underground system is Waterloo station, with 90 million rides per year. It`s followed by Oxford Circus and King`s Cross Street Pancras.
The following 2 maps of the London Underground give you all the info you need about the Tube system at a glance.
Here is a London subway map showing the same Tube lines as above but this one is focused on the tourist attractions in Central London. You can see some icons for places on interest on the map. Just be careful about the outlying areas that are cut off from this map.