This is St Paul's from just near my work.
If you then walk around St Paul's and towards the Thames, you come to the Millennium Bridge (which the British Government built for the 2000 celebrations and then took a lot of flak for as the the bridge was architecturally flawed and wobbled). From the bridge you look one way and see the Tate Modern, and the other way, back north to St Paul's.
Here's a better view of the bridge itself.
The galleries and museums are all open till 10pm. I wasn't allowed to take photos in the Tate, but they have some really interesting and sometimes controversial art (being a modern art gallery). A lot of things that you think a 6-year-old could create, but also some really amazing things, and some famous works from people like Andy Warhol, Picasso, Frida Kahlo and Joan Miro. I particularly liked the photos by an artist called Francesca Woodman - a bit depressing, especially because she killed herself at 22 - but very original. So anyway, I took a photo of an installation outside just to get one art photo, and also one of me because I know how dull photos with no people can get. I also took a shot of the escalators because they were kind of beautiful all on their own.
And finally a night shot of St Paul's on the way home to the Tube.