Herod’s enormous building project on the Temple Mount, whose implementation continued for many years, was actually planned and carried out in three stages: in the first stage, prior to any activity on the Temple Mount itself, the Antonia was erected which replaced the Hasmonean Baris fortress that stood northwest of the Temple Mount.
In the second stage, the temple that had been constructed during the “Return to Zion” (which included improvements conducted over the years) was replaced by a new building. Along with the temple the courtyards, bureaus and gates that surrounded it were most probably rebuilt, but insofar as these are concerned and unlike the temple itself, Herod and his architects were free to plan them as they saw fit. Undoubtedly, the temple was located in the exact same place as it stood during the First Temple period. At this point the framework for the Temple Mount probably continued to exist as it had from the end of the Hasmonean period, namely as a complex surrounded by a wall with stoae on several of its sides. (There is no reason to assume that during the year and a half it took to construct the temple Herod split the effort between building the temple and expanding the Temple Mount).
In the third stage, upon the completion of the temple and the courtyards, Herod began to plan and implement the enlarging of the Temple Mount’s boundaries. Unlike rebuilding the temple, he now had to cope with a number of factors: 1) he had to take into account such existing elements as the Antonia, on the one hand, and cleaning and preparing the area available for construction on the other; 2) challenging topographic conditions on practically every side; 3) arranging access and approaches to the temple for the masses during the construction work; 4) implementing the monumental construction of the walls. During the planning process the existing eastern line of the Temple Mount was left unaltered. The extent of the expansion to the south was probably dictated by the size of the royal temple court. The expansion to the west was most certainly determined by various considerations, as was that to the north, but here Herod compromised with the presence of the Antonia that he himself had built years before. As a result of the “compromise” the royal citadel protruded c. 65 m into the area of the plaza.
I believe enlarging Temple Mount in the third stage consisted of a process of expansion whereby “strips” were added to the existing Temple Mount (that of 500 x 500 cubits) rather than a sophisticated planning operation involving angles and predetermined proportions or for that matter planning according to axes. I believe the only possibility for any maneuvering (if there was any at all) was in determining the location of the entrance to the Temple Mount itself, halfway between the eastern and western stoae and between the royal courtyard in the south and the northern stoa (east of the Antonia).