me too - well Barcelona for a week then London. If you're into walking around, the Thames embankments are great photo ops for city-scapes, especially from the many bridges such as Waterloo and the pedestrian "Millenium bridge" around the "South Bank" area.
I think the classic/must-see would be get off the tube at Westminster station (Big Ben/Parliament, Westminster Abbey) -- head over Westminster bridge, once over, on the right you can go down to the embankment and you're right across for classic shots of the House of Parliament etc, then walk back along the Thames in the other direction (towards Waterloo Br. & the South Bank) - you can then see Shakespeare's Globe etc, cross over the pedestrian bridge to St. Paul's (again lovely views), and then take St. Paul's tube if you've had enough walking. Or if you're adventurous continuing walking to Tower Hill (Tower of London of course) - then maybe take the DLR to Greenwich "Cutty Sark" and walk around there.
