The Underground Train Network
The Underground is the fastest way around London with an abundance of stations conveniently dotted within central London. Most people in London use it, although during rush hour periods it can get very crowded.
Underground trains on all lines run every few minutes between 5.30 until 24.00 - 00:30 Monday to Saturday, and between 7.30 - 23.30 on Sundays. You can get a map for the entire Underground system (and British Rail trains that run within London) free of charge from all train station ticket offices. No smoking is allowed on the Underground and Buses, including within the stations themselves.
Fares.
The Underground and Bus networks are divided into 6 fare zones. The cost of travel is determined by which zones your journey takes you through. All of central London and the Docklands business area is within the central zones 1 and 2.
There are several ticket options, ranging from a single one-way ticket to your destination, to an 'LT Card' and a 'Travelcard' which gives you unlimited use of all three transport systems for the duration of the ticket.
Understanding the Underground network map:
Each underground line has its own name and colour, and each station is marked in order on its line. Stations which are marked with a black circle indicate that you can change lines at that station.
For example, if you were travelling from Heathrow Airport Terminal 4, and wanted to get to your Hotel which is at Bond Street. You would take the Piccadilly Line (dark blue) until you got to Green Park, and then change onto the Jubilee line (grey) to Bond Street.