If it works, use it. This is the driving basis for many engineering applications. This belief extends to structures as well. For example, in the aqueduct which is a fractal application segment seen in Pont Du Gard illustration below. At the time of its initial design and construction the arch was the most efficient and common way of support a large structure. The load bearing capabilities combined with the reduced weight of a solid structure made it very appealing. The repetition of the pattern to extend the benefits of the load bearing structure became very apparent and accepted.
In the following case it can clearly be seen that the application of arches to this structure was quite extensive. The arches serve the same function throughout but they range in position and in scale. This same type of idea can be extended to a variety of other structural conventions.
This is another example of the same expansion characteristic of humans in their domiciles as featured in the Urban growth section of the "Fractals in Nature" page. It is simply more efficient (less work and materials) to use an already existing wall and create three new walls that it is to make four entirely new walls.
Vertical expansion of buildings (multistory buildings and "skyscrapers") utilizing a common foundation and allowing for high proximity of structural space is also a similar variation on the previously described theme of fractal growth characteristic.
The Eiffel Tower could be considered a fractal, with the object on the bottom as its initiator. The interesting thing is that "fractals" had not been technically invented at the time that the Eiffel Tower was designed or built. Instead "fractals" were only invented and the term coined in the 1970's by Benoit Mandelbrot. This is just more proof that fractals are a very intuitive design. The intuitive understanding of fractal design clearly predated the formal adoption of fractals as a recognized field of study. The extensive use of fractal patterns and design concepts throughout the development of modern civilization points out that it only requires a certain amount of familiarity before the benefits of this system can be utilized in the world around us in many forms.