Here is an anonymous Italian Renaissance painting of an ideal city painting now preserved at the Walters Gallery in Baltimore. Its width is considerably greater than its height.
More specifically, its width is 2.828 times its height, or two times the square root of two. This can be seen by unfolding the diagonals of two squares set on its outer edges. Note that the right margin of the left square aligns with the central axis of the amphitheater in the distance.
Several key elements in the painting can be found by tracing lines of 30-degree and 60-degree slope upward from its outer lower corners. The right margin of the amphitheater aligns with the vertical where the 30-degree line cuts the left arc, and the left margin can be found by reflection. The baptistery at right fits into a nearly equivalent frame, although it is compressed slightly to the right.
The front corners of the palaces in the foreground can be found by first drawing a yellow horizontal through the point where the 30-degree orange line cuts the axis of the amphitheater, and then drawing yellow verticals through the circled points halfway between the intersections of this horizontal with the 45- and 60-degree lines.
The rear corners of the palaces are exactly halfway between the panel margins and its center, as the green verticals indicate, and the green horizon line can be found at the level where the rising green lines of 30-degree slope cut the orange margins of the amphitheater and the baptistery.
The top edge of the right-hand palace can be found by running a blue line from the vanishing point to the top of the yellow vertical describing the right-hand palace corner. From the point where this blue line cuts the orange line of 60-degree slope, a blue vertical can be dropped to find the axis of the column in the foreground, and a similar construction also works in the left half of the panel, even though the palace there is shorter.
The perspectival lines in the pavement can be found by connecting the vanishing point to already constructed points in the foreground, and a similar scheme located at the front edge of the platforms on which the palaces stand.
This painting is the property of the Walters Art Museum in Baltimore, Maryland.
This analysis was based on the image: