In particular, it is possible to reconstruct relatively precisely the rise of the Roman segmental arches on the basis of the angles of the inclined stone supports at the springing level. Thus, the third arch originally described a circular sector of 95°, which points to a span-to-rise ratio of about 4–5 to 1 for the other segmental arches. This value is supported by de Labordes' engravings which depict an intact Roman segmental arch spanning the adjoining fourth bay as late as the early 19th century. Along with other early examples, such as Limyra Bridge and the Ponte San Lorenzo, the Alconétar Bridge therefore ranks among the oldest segmental arched bridges in the world. Its existence demonstrates that, in contrast to what had previously been widely believed and taught, Roman bridge builders possessed intimate knowledge of flattened arches.