THE FIBONACCI SPIRAL
The Fibonacci spiral is found throughout nature, from the spiral in a shell to the shape of a tornado from above. However, this goes further than literal spirals. The Fibonacci spiral is produced from the Fibonacci sequence, the resulting shape is the same as can be seen in the section of the building (the second image). This spiral works off the golden ratio, which states that a line, for example, cut into two should have the the longer part of the cut line divided by the shorter part equal to the whole line divided by the longer part. This explained visually in the image at the bottom.
The ratio was used a lot by the Romans and can be found in their architecture too. This example uses the spiral as its focus though and is a nice way of relating the structure to nature.
I think it is definitely worth baring in mind that to make a design feel natural, the subtle influences can be just as important as the direct appearances. Simply cladding any shape or building in wood may not always make it seem natural, but i feel that to design with the same patterns that nature contains would create something which fits far better into that environment.