The Golden Rectangle and the Amazon River

Successive Golden Rectangles dividing a Golden Rectangle into squares (Mouth of the Amazon River in Brazil, Satellite image).

A golden rectangle is a rectangle whose side lengths are in the golden ratio, one-to-phi, that is, approximately 1:1.618. A distinctive feature of this shape is that when a square section is removed, the remainder is another golden rectangle, that is, with the same proportions as the first. Square removal can be repeated infinitely, which leads to an approximation of the golden or Fibonacci spiral.

Fibonacci numbers (0,1,1,2,3,5,8,13,21,34...) are a sequence of numbers named after Leonardo of Pisa, known as Fibonacci. The first number of the sequence is 0, the second number is 1, and each subsequent number is equal to the sum of the previous two numbers of the sequence itself.

The Amazon River of South America is the largest river in the world by volume, with a total river flow greater than the next top ten largest rivers flowing into the ocean combined. The Amazon, which has the largest drainage basin in the world, accounts for approximately one fifth of the world's total river flow. Because of its vast dimensions, it is sometimes called The River Sea. At no point is the Amazon crossed by bridges. This is only partly because of its huge dimensions—for most of its length the Amazon is not so wide that a modern bridge could not span it—but also because, for most of its length, the river flows through tropical rainforest, where there are few cities and even fewer roads.