I've been to the Museum of London, the Wallace Collection and the Globe and they're all really, really interesting. You've only got three days so you won't get in everything that you want to but any of these would be well worth your time. The Wallace Collection is free which might sway your decision, located just a few blocks north of Oxford or east off Baker Street on Manchester Square. There are paintings, miniatures, three great rooms of armoury, antiques, and a lovely courtyard restaurant.

I am fascinated by the history of London so i enjoyed the London Museum at the Barbican. It's set up so that you can follow the history from the early roman era up to the 20th century. The Globe, on the South bank of the Thames has interesting displays on theatre history south of the river, with interactive displays and if you're there at the right time, they also do an inside tour of the theatre itself which is free. I can't remember if there's an admission price to the Globe but i'm pretty sure there is to the museum of London. The websites will tell you anyway.

St. Paul's is lovely inside, very elaborate. There's a fee for this i think. We also paid the extra fee to climb up into the dome. Not for the faint of heart if you go to the balcony on top of the dome, though. The platform was not very wide and only a wrought iron waist high guard rail around it as i recall.

Another great small museum is the Sir John Soane museum on Lincoln's Inn Fields. Fascinating, free (ring the bell to get in), and small enough to do along with something else.

Diane Johnston Halifax, Nova Scotia