United Kingdom
Get a Zone 2 Travelcard rather than Zone 1. Then go to Westminster Pier and take a boat to Greenwich (£6.80 single). There is a very informed commentary on all the sites you pass. When you get to Greenwich you can visit the Cutty Sark, market and Maritime museum, then use the Docklands Railway to get back and see all the modern sights of the East End.
To really appreciate the city in style, either take a canal boat from Little Venice to Camden, or cycle from Maida Vale all the way to Kings Cross along the canals. Or go the slow way, by foot! You can stop off at any point to appreciate cafes, pubs, parks, city streets, London Zoo or Camden Market. Lush!
Nice place to start the journey is from the top of Golbourne Road near Portobello, or get on from Westbourne Park Tube and then just keep going until you can´t take it anymore!
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