Final answer:
Concrete was the structural material that enabled the creation of the grand Sanctuary of Fortuna Primigenia, exemplifying Roman power through its innovative use in extensive terracing and complex design.
Step-by-step explanation:
The structural material that allowed the architect of the Sanctuary of Fortuna Primigenia to construct such an impressive representation of Roman power was concrete. This material was essential for Roman builders, allowing them to create structures that were not only taller but also more complex and durable. The use of concrete enabled Roman architects to move beyond traditional post-and-lintel construction methods, facilitating the innovation of covered ramps, large terraces, barrel vaults, and much grander designs overall. In the case of the Sanctuary of Fortuna Primigenia, the use of concrete in conjunction with the strategic terracing of the complex played a crucial role in manipulating the visitor's experience and allowing for the creation of an expansive compound woven together with various architectural elements.