London transportation system is one of the oldest and easily described as the easiest in the whole world
Oyster Card or Travel Card are your keys to all of London transportation means
You need to buy Oyster card or travelcard online here:-
Oyster card issuance is approx.. 3.25£ then you charge it (top up) the amount you want in any train station, tube stations and public kiosks), however if you are spending 1 day in London, start with 15£, 2 days top up 30£, you credit will never expired.
Travelcard is valid for one week and it costs 33£ for zone 1, 2 (Central London where most of the city attractions are located).
From London Heathrow to City centre, we recommend using Heathrow express for 17£ per way, will take you in 20 minutes to Paddington station where all of London is accessible and easy to reach
Landon is covered by approx.. 11 underground lines, wherever you are heading, you will most probably take the underground, here is the map for it.
You will not get confused, check where you go, take the underground from where you are, get off where there is interconnection with another line, get on the other line and enjoy your trip
London interactive map