This is a well known picture that has been done to death. I am sorry, but it is such a great shot so please allow me the indulgence. There is only one place to stand to get this so everyone’s shot looks the same. The only difference being the characteristics of the lens that is used.
This shot was made with my 17-40mm lens at 17mm. On my 5D Mark 2, that is a “real” 17mm so pretty much as wide as you can get without going to a fisheye.
This stair case is kinda mesmerizing. When you gaze down into it you don’t realize it is a double spiral! You have this nagging sense there is something wrong, but cannot place it. Then all of sudden, you see it! There are two “loops” that spiral down – follow them with your eye. When you go down here, it is deceptively steep! I guess because of the double helix-like-thing, it needs to allow enough room for the other loop.
This stair case is in the Vatican, in the museum. At the top (where this picture is taken) is a “good old souvenir shop”. Yes even in the Vatican has commercialism found a way in.