Sentence:  […] the way that the greatest width of the interior of the Flavian amphitheatre would be ascertained, if a line were drawn from one of the <WSD>vomitoria</WSD> of the west side, in the uppermost story, to the eastern <WSD>vomitorium</WSD>, precisely facing it. 
Meaning of the word marked with <WSD> tags:  A passage located behind a tier of seats in an amphitheatre used as an exit for the crowds