I have already posted a photo of the dome of St. Peter's from the inside. This is what you see when you stand on top of the dome. The climb up is a bit strenuous but well worth it. Though I would suggest you consider going up in the morning because you can avoid the heat and the crowds.
You can see two countries in this photo - Vatican City and Italy. The "border" is a white line at the open end of St. Peter's Square (which is actually an ellipse). The "square" and the colonnades that enclose it were designed by Bernini, who also designed the baldacchino visible in my interior shot.
What was I thinking when I got to the top? I was thinking that it's a good thing that there is a sign by the dome ticket window warning people with heart problems that the climb may kill them. I was also thinking that it's too bad Michelangelo, who designed the dome, didn't live to stand where I was standing. I wonder if Pope Benedict has been up here?
Do want to view a narrated video of this photo? Try going here. (This is a bit of an experiment and it is clearly un-rehearsed!)
Canon 5D 1/640s f/5.0 ISO400 24mm