For travelling the 'Tube' buy a 'travel card' or an 'Oyster Card'London's underground, better known as the 'Tube' transports over 1 billion people around the English capital every year. There are 12 lines in operation and because many of the city's top attractions have their own stops, you'll definitely use it at some stage.For buying tickets you should buy one of these two:Off-peak travelcard for zones 1 and 2: Costing just over £5, this will permit you unlimited travel on the tube within zones 1 and 2, which should be enough for any visitor to the cityOyster Card: These can be picked up at tube stations. They cost £3 and work on a pay as you go basis. Each journey then costs £1.50, but there is a 'capping' scheme where once you use a certain amount, it will stop taking money off your card. They make travelling on the tube cheaper, easier and quicker.