"The Mona Lisa," indisputably Leonardo's most famous painting, is full of Golden Rectangles. If you draw a rectangle whose base extends from the woman's right wrist to her left elbow and extend the rectangle vertically until it reaches the very top of her head, you will have a Golden Rectangle.
As you can tell, both pictures are closely related, and both represent the golden ratio.
In the following picture, phi is clearly represented:
Here phi is represented by the golden ratio and the golden rectangles.
Here, as you can tell by this diagram, the pentagram or the golden star, is represented. In the Golden star, each intersection of edges sections the edges in golden ratio: the ratio of the length of the edge to the longer segment is φ, as is the length of the longer segment to the shorter. Also, the ratio of the length of the shorter segment to the segment bounded by the 2 intersecting edges (a side of the pentagon in the pentagram's center) is φ.
Here is an example of the 3D Fibonacci prisms that also show the golden ratio: