Hi Masha, there is so much to do in London!
Attractions: Buckingham Palace, Tower Bridge, Tower of London, Houses of Parliament (Big Ben), London Eye
Museums: British Museum, National Gallery, Tate, Natural History Museum
Parks: Regent's Park, St.James' Park, Hyde Park
Entertainment and leisure: Chinatown, Soho, Covent Garden, Leicester Square, Notting Hill, Brick Lane (Indian food), pubs all over London
Have a great trip!