Waterloo is a good starting point. If you go towards the river, you can look across and see Somerset House to the east just a bit, and Parliament to the west. I like to go from Waterloo to Westminster Bridge, then cross the river at the bridge to see Parliament, Westminster Abbey... etc. From there I can either go east to Somerset House, or go west to St James Park, Buckingham Palace, Primrose Hill... and so on.
This is Somerset House:
Somerset House is a great place to go for art exhibitions - so check them out and see what's on when you visit.
Keep walking down Southbank towards Parliament and you end up go by the London Eye, the Southbank Centre, Aquarium and City Hall. I highly recommend doing this twice - once during the day, and again at night. The London Eye, City Hall and Parliament should all be seen at night when all lit up. You can get great pictures from Westminster Bridge.
So put your walking shoes on, grab a map and get going.
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