Final answer:
The Romans used arches back to back to create a structure known as a vault, which allowed for larger interior spaces and stable, durable construction. This technique led to the development of innovations such as the groin vault and the large-scale dome, exemplified by the Pantheon, showcasing Roman architectural ingenuity.
Step-by-step explanation:
The Romans were architecturally inventive in the way they placed arches back to back to form a vault. By doing so, they were able to create larger interior spaces and tunnels, such as those used in aqueducts like the Pont-du-Gard. Additionally, the innovation of the true arch allowed Romans to construct impressive structures like the groin vault, which further expanded interior space, and ultimately the development of large-scale dome structures, exemplified by the Pantheon's wide, open space.
Roman architects were also known for their use of concrete in conjunction with arches, which resulted in durable and aesthetically pleasing buildings. These constructions showed a keen aesthetic sense, combining functionality and form, which played a vital role in architectural history. This architectural method was not just used for practical constructions but also used in public spaces like basilicas, reflecting their mastery in the architectural arts.