Is London a "pretty walkable city?" Yes it is. Use Google maps satellite view https://maps.google.com. Type in Big Ben, London, United Kingdom. When the birds eye image appears use the zoom function on the left part of the screen (below the little golden man) to zoom in and out. If you zoom out one click and use the < function (to widen map size and include the Palace) you'll discover an overhead view that shows you can walk from Big Ben and Parliament across the Wesminster Bridge to the London Eye, walk back and over to Westminster Abbey and from there cross the road over to Birdcage Walk and follow it up to Buckingham Palace. VERY walkable way to see many of the "top sightseeing spots." You could also walk from Parliament Square up Whitehall pass the Horse Guards and #10 Downing to Trafalgar Square, National Galley and St. Martin's. From there easy few blocks to Leiscester Square and over to Convent Garden. IMHO walking is the best way to "see" London. Merely depends on your stamina level, comfortable shoes and sense of direction. BTW using Google Maps street view is a great way to see what's nearby your accommodation. Bank ATMS. Pubs. Markets. Tube Stations. Coffee. GREAT research tool and research is the key to happy traveling.