Running After Antelope question response

Explain the meaning of "They had the structure of the Golden Gate Bridge-a high, sinewy arch with built-in springs and pulleys, and long toes stretching out for purchase." What literary device is shown here? (21)

        The author uses these lines at the end of a paragraph which he spent describing how beautiful and aesthetically pleasing this girl was. At the end we find these lines comparing her feet to the Golden Gate bridge. Several literary devices are cooperatively at work here. Most obviously is the use of imagery in which the reader develops an almost majestic and beautiful picture of this woman in their minds. In addition to the imagery, there is the metaphor or her feet being like a bridge; not just any bridge but the Golden Gate Bridge. Her tendons and muscles in her feet also are implied to be like the cables of the suspension bridge. The last device while maybe not particularly important is simply the allusion to the Golden Gate Bridge.