Colonnade Of St. Peter's Square, Vatican, Rome. Editorial Image

This specific design meets the requirement to create a space that is visually enclosed yet materially open, allowing for effective occupancy and clearance. As an observer moves through the square, the substantiality of the overlapping columns conveys the impression of an enclosed area. However, when the observer stands at one of the two focal points, their perception shifts entirely, as these points align with the ellipse's foci, offering a clear view of the space beyond the ellipse.