It is unclear to archaeologists where the Shuk Elyon was. Generally speaking Elyon is a topographical concept as in Beit Choron Elyon which was higher than the Tachton (and which has been commemorated in the names of the Arab villages in Beit Choron to this day). Thus the Shuk Elyon would be higher than the lower one which presumably was to be found in the lower city -either under Temple Mount or even further down in modern-day Ir David. But was it at the highest point? The Gemara here says that Kazran shel Goyim was the place of Shuk Ha'Elyon and some explain that this Kazran was not a person but a Kasra or castle in Latin. Thus this would be the elevated Shuk adjacent to the castle of the gentiles- which in the time of the Temple was near the Tower of David, the site where the 10th legion was camped and the highest point in Jerusalem.

Since the modern-day Arab Shuk descends from that point until it meets the Kardo, I am tempted to say that this is the upper shuk both because of its elevation and its proximity to the Kazra shel Goyim -The Rambam in his commentary to the mishna says that "Goyim lived there" and this fits with the area of the 10th legion's camp. Others say that the shuk was a place for impure people to gather, presumably near Goyim who would not care about their impurity.

The Kardo, as its name suggests, was not the highest region and was not a place for gentiles and impure people but rather the center (as in cardio- the heart which has four chambers and a center, the cardo is at the center of four different roads which cut Jerusalem into a heart-like shape). It may well be the Shuka DeTziyon mentioned in Brachos 60a.

Yoel Domb