There are travelcards for travel within London on all forms of transport: trains (within London), the Tube, buses, Docklands Light Railway, et al. The best deal is the seven-day card, even if you will only be there six days. It's available in any Tube station at the window, and requires you to give them a passport type photo which they use to create a special ID card to go with the travelcard (should you be challenged to prove it's yours). You can either take a photo with you (even a photo from your own digital camera) or use one of the photo booths in major Tube and railway stations. If you're going to Paris, too, take several photos since you can do the same for the weekly Carte Orange (which is, unfortunately, a calendar week card).

To not confuse the seven-day travelcard you buy in London with the Visitor Travelcard you can buy from North America; it's pretty much agreed that card isn't much of a bargain.

In general, a travelcard for Zones 1 and 2 is what you want.

Regards, DAVE HATUNEN Tucson Arizona, out where the cacti grow