AbstractAs already indicated by Galileo, the laws of rescaling for load-bearing structures do not follow the simple geometric proportion because the structural weight increases more than the structural capacity and can equally lead to an effective loss of stiffness. Developing the theory originally proposed by Stüssi, the structural capacity of various materials are compared on the basis of performance indexes, such as specific strength and specific stiffness. This highlights how the structural weight increases as a function of the service load for various static schemes, dictating a theoretical limit for the structural size. Worked examples are presented in the fields of civil, marine, and aerospace engineering. Solution-spun carbon nanotube fibers appear promising because they are sustainable green materials whose capacity is superior to the best steels and comparable with the state-of-the-art carbon and Kevlar fibers. It is expected that the continuous improvement of the production techniques can bring their performances close to the theoretical limit of the constituent carbon nanotubes (CNTs), allowing the construction of superstructures not even imaginable today with the currently available materials.