London, capital of England. A lot of attractions especially when you are at the central London. What you have to do is get yourself a Oyster Card. (3pounds for a card and top up as you like).
By having the card, you could take Double Decker Bus (1 Pound per time), or underground or tube (price depends on distance).
There is a route for the heritage visit from where I stay- St. Paul's Cathedral to Millennium Bridge, reach the Tate Museum, walk on the south of the Thames river bank, reach the art gallery, then to the Aquarium and London Eye, cross the Westminster Bridge, you will see the Big Ben, House of Parliament , Westminster Abbey, Horse Guard Museum, National Gallery and Trafalgar square. At this junction, you could either turn left to the Buckingham Palace, or turn right to the Aldwych. If you go to the Buckingham Palace, you should not miss the Green Park and St. James Park. If you are going towards Aldwych, there are a lot of theaters and you should go for at least a show which is really famous in London. (But I didn't go because I am a budget traveller which need to save $ ^.^)
From Aldwych, you could continue walking in within 10 mins, You will meet the starting point again.
St. Paul's Cathedral from the Millennium Bridge.
Tate Museum. (Free)
View from south bank of Thames River.
Eye of London and London Aquarium.
House of Parliament, Big Ben. ( Actually Big Ben is part of the House of Parliament)
Westminster Abbey.
Horse Guard Museum.
Trafalgar Square and National Gallery.
Buckingham Palace (and the monument in front of it), Green Park and St. James Park.
Theaters around the Aldwych and scene along the road. 
