Tourists visit St Peter's Square rather with a touristical guide than with a measuring tape with a lenght of more than 200 m to control wheater the square is elliptal or not. [br]Looking to the plan, you can easily see that Bernini desigens St Peters Square as an ovaal according to the well known scheme of Serlio based on equilateral triangles.[br]You can notice that the boundaries of the colonnade match with the boudaries of the circular arcs if the smallest size, to which a finishing construction is added.

The centers of the two red circular arcs of the oval are marked on the square by a stone bearing the inscription [i]centro del colonnato[/i]. Indeed they are what they are: centers of circles.[br]In contrast the foci of the ellipse that approximately matches the oval roughly correspond with the fountains on the square