It has been reported in the media (see for example BBC news and the Jerusalem Post) that excavators Ronnie Reich and Eli Shukrun have excavated a large section of the drain that was located just below the Herodian street. This drain was constructed, so that the rain water that fell on the street and the liquid sewage of adjacent buildings could be disposed off. Here is a picture of the drain (AP Photo/Emilio Morenatti):
Parts of this drain have been investigated by Charles Warren (1867-1870) and other sections have been excavated by Bliss and Dickie (1894-1897), Johns (1934), Kathleen Kenyon (1961-1967) and Benjamin Mazar (1968-1978). The section found by Mazar below Robinson’s Arch was vaulted and believed to have been a relay of the original drain which had been cut by the south-west corner of Herod’s temple Mount, see this picture from The Quest, p.56:
Warren also investigated a much earlier drain, lower down in the Tyropoeon Valley, so that we know of two different drainage systems. Together with the relay mentioned above, there are three different phases in this drainage system, which indicate three different building phases in the construction of the Temple Mount, see The Quest, pp. 233-235.
The present excavators have not yet provided a map of the excavated drain, but only said that is was between the Temple Mount and the Siloam Pool. In the 1890′s, Bliss and Dickie discovered a large section of the Herodian street near and to the north of the Siloam Pool. This section alone shows that the main street, which, we believe began at the Damascus Gate and followed the Tyropoeon Valley and exited at the South Gate – see map below. On this map we have plotted the street section that was found by Bliss and Dickie in grey with the drain in red:
As the excavators have been digging in the vicinity of the Siloam Pool, the newly found drain is likely to be located just north of the pool. This find received a lot of media coverage because of the remarks made by the excavators that this drain may have been used by people who tried to escape the Roman destruction of Jerusalem in 70AD.