Hi there.....I put your picture into Photobucket and played around
with it to try and bring the circle out more.
This is it after using Auto Fix, putting the contrast and brightness
up a bit...and giving it an orange/beige tint.
Nice capture, by the way.
I wonder if it has got anything to do with the Olympic Village being
built? Could it be 'something' to block out satellite pictures?
Security for the 2012 Olympics must be a nightmare for the organisers.
Pure speculation.
Also..there seems to be a definite blob/sphere on the 'circle' at the top.
edit to say...LOL...I've made it look a bit of a mess now...I've only just seen metaw3's post
and I took it from the enlargement that seeingterra did....