UK- London
How about?
Day trip - Piccadilly Circle including Buckingham Palace, Trafalgar Square, etc
And don't miss if you have time - Hyde Park, Big Ben, Walk along Thames, Cruise in Thames, Walk over the ped bridge over Thames, Westminister Abbey
Evening trip - London Eye for Giant Wheel
Day Trip - Madame Tussauds for Wax Museum
Attractions Map
How to reach London downtown from Heathrow Airport?
Places to visit in London for a short stay of 1-3 days:
The Tower of London
St Paul's Cathedral
The London Eye
Buckingham Palace
Tower Bridge
Trafalgar Square
Piccadilly Circus
Westminster Abbey
Downing Street
Horse Guards