via delle Arene; an enclosed green space, sort of a cross between a park and a vacant lot, behind a tall spiked fence to my right; no entrance anywhere, circumnavigated the area back up a commercial boulevard on the other side; investigated alleys of chop shops and the areas behind them looking for the Northwest Passage; and finally, after having deambulated clockwise some 345°, spotting an apartment building where the gate was open because an oral surgeon worked there.
From the back yard of that building I got my only glimpse of a lumpy sward of grass with below grade a few vague outlines of what I think is the cavea; my camera thru the one place in the fence not too badly blocked by trees, and presto! this may be the only image of the amphitheatre of Milan on the Web....