The Descending Shaft from the Paved Street to the Channel. Two walls, 3.7 m apart, which are parallel to the Western Wall of the Temple Mount, were identified when clearing the collapse in this section. Segments of these walls were identified by the Mazar and Ben-Dov expedition. These walls were built of ashlar courses, arranged in various ways, with fieldstones and a few small stones inserted in the gaps, without mortar. Much of the western of the two walls was found dismantled, as it was situated in the area of Warren’s shaft and its remains are visible in the shaft’s northern section. The eastern wall was well-preserved. These walls were evidently built of stones in secondary use that were probably dismantled from the walls of dwellings that had been expropriated to implement the expansion project of the Temple Mount by King Herod.  
At the bottom of Warren’s shaft below the street, a small rectangular cavity hewn in the bedrock, and accessed by two steps from the east, is located (Fig. 1). This space was apparently not used as a ritual bath (miqwe) because it is not plastered, the steps are quite narrow and the bottom step is fairly high above the bottom. This space, like other nearby cavities and installations, was part of a residential building that existed in the area prior to the expansion of the Temple Mount.
Warren’s Northern Tunnel—From the Shaft to the Western Wall. Warren had dug a tunnel that began at the breakthrough point of the shaft in the pavement of the street and continued east to the Western Wall. To dig the tunnel, he breached an opening through the eastern wall of the two parallel walls (wall thickness c. 0.9 m; see the ‘eastern wall’ below) because that wall was located right underneath the eastern curbstone of the street above it; both the street and the wall were aligned north–south. The entire breadth of the wall’s structure could be seen in the northern section, which was straightened in this excavation, as well as the soil fill that was deposited between it and the parallel wall to its west, and between it and the Western Wall. Undoubtedly, the Western Wall and the two parallel walls were built first and only then was the soil fill deposited between them. The soil fill contained a large quantity of stone chips—stone dressing debris that was left from the cutting of many stones during the construction of the Western Wall. The western face of the ‘eastern wall’ was built extremely close (c. 0.1 m) to the eastern end of the southern of the two voussoirs that was wedged inside the large drainage channel. Since the wall is standing in its entirety near the fallen stone, one can assume that the stone collapsed first and only afterward the wall was built. It seems that the ‘eastern wall’ is an underground retaining wall, similar to a stylobate, but the curbstones of the street above it never bore columns and they did not require such a strong underground support. Furthermore, the street’s curbstones are not placed directly on the underground wall, but at a height of c. 0.3 m above it.
The Excavation near the Western Wall. Three short walls (width 0.7–0.9 m) that extended from the ‘eastern wall’ and whose construction was similar to the latter, were revealed in the area between the Western Wall and the eastern face of the ‘eastern wall’ (width c. 2.1 m). The walls were dismantled and the soil between them was excavated to the bedrock level along the Western Wall. The bedrock surface is uneven; it is leveled in the northern and southern parts, while in the middle, it has a depression where three large stone slabs were deposited to straighten the surface.

Warren’s Southern Tunnel—From the Large Drainage Channel to the Western Wall. Warren had dug another tunnel, c. 10 m from the northern tunnel, which began at the large drainage channel and continued toward the Western Wall, crossing the ‘eastern wall’. A hewn opening in the bedrock was discovered near the upper eastern edge of the large drainage channel. This opening led from a vaulted, rock-hewn room to the upper part of a ritual bath (miqwe) from the Second Temple period. The miqwe was next to the opening, negating it; and therefore it postdated the opening. Remains of two rock-hewn steps in the original entrance to the ritual bath from the east were preserved. The miqwe was filled with medium-sized fieldstones, atop which the southern continuation of the ‘eastern wall’ was built. The upper edge of the miqwe was visible; it had rounded corners and was coated with gray plaster. An upper step was also discerned inside the miqwe. The ceiling of the miqwe was an ashlar-built vault, several stones of which were preserved in the western side, including the vault’s springing stone.
The vaulted rock-hewn chamber was located west of the large drainage channel, opposite Warren’s southern tunnel. Its shape is irregular and large bedrock chunks, whose quarrying was incomplete, were visible on the bottom and in the corners of the room. The ceiling in the western part of the room is flat bedrock that descended to the west, while its eastern part, as far as the large drainage channel and above it, was covered with a stone vault (Fig. 2). The southern part of the vault was preserved in its entirety, whereas its northern part was breached by a large stone, still stuck in the vault, which was covered by the paving stones of the street above it. It seems that the stone fell into the vault because of the Robinson’s Arch collapse. Another stone that originated in Robinson’s Arch was discovered inside the room; it is placed today off to the side.
The Large Drainage Channel. This section of the channel (width in excess of 1.05 m) is bedrock-hewn, its sides are vertical and the bottom is flat; the ceiling is an elongated vault built of five stones. The channel twists and encircles the southwest corner of the Temple Mount. Warren documented two large voussoirs that were stuck in the top of the channel. The channel’s vault adjoins the northern voussoir that is wedged in the top of the channel. The vault also abutted from the north the broad vault that covered the rock-hewn chamber. It therefore seems that both the voussoirs and the hewn room had already existed in the area when the drainage channel was covered with the elongated vault. There is also no doubt that the voussoirs collapsed and became stuck in the top of the channel before the street was paved. That being the case, these voussoirs did not fall when Robinson’s Arch collapsed after the destruction of Jerusalem in 70 CE, but probably disintegrated in a work accident during the construction of the arch. The rock-hewn room and the ritual bath to its east had been part of a dwelling located in the area before the Temple Mount expansion project was begun during King Herod’s reign.
Farther to the south, the channel crosses a circular cistern (Fig. 3), which is the southernmost of several cisterns that Warren discovered. The bottom of the cistern, sloping slightly to the southeast, is flat and c. 1 m lower than the bottom of the channel. A right angle is formed between the vertical side of the cistern and its bottom; this angle differs from the Second Temple cisterns where the joint between the side and the bottom of the cistern is quite curved. The cistern’s ceiling is flat and descends to the southeast. A hewn opening in the ceiling is surmounted with a long hewn, narrow shaft for drawing water, which reached the surface. The street pavement passes above the shaft and negates any possibility of drawing water from the cistern. The entire cistern is coated with well-preserved, yellowish brown plaster. A large bedrock block inside the cistern is partially coated with clay-plaster; it seems that this was part of the cistern’s side that had been breached when the drainage channel was connected to the cistern. If so, it is clear that the cistern predated both the drainage channel and the street pavement above it. Although no stratigraphic connection is traced between the nearby miqwe and the rock-hewn chamber on the one hand, and the cistern on the other, it nevertheless seems that the cistern is significantly earlier than both. The clay plaster lining the cistern negates any possibility that it was contemporaneous with them. Based on the plaster, it seems that the cistern dated to Iron Age II.
Nine phases of relative chronology can be counted in the region of Robinson’s Arch since King Herod pondered expanding the Temple Mount.
(1) Formulating a plan for enlarging the Temple Mount.
(2) Dismantling dwellings situated at the bottom part of the bedrock slope that descended from the Upper City to the channel in the Tyropoeon Valley, i.e., the western side of the valley.
(3) Marking the corners of the Temple Mount and building the first course of the Western Wall and the Southern Wall.
(4) As a result of constructing the first course of the Temple Mount’s southwest corner walls on the western slope of the Tyropoeon Valley, the gorge was blocked and a large puddle of rainwater, which could not flow south in the valley, was created in the wadi during the first winter.
(5) Quarrying a wide drainage channel that bypassed the corner of the Temple Mount in a large curve. In this phase the elongated stone vault did not cover the channel. The rainwater flowed in the drainage channel and continued south in the open channel to the Siloan Pool.
(6) The beginning of the construction of Robinson’s Arch. It seems that an accident occurred in this phase and parts of the arch collapsed. Two voussoirs became wedged in the top of the channel and it was evidently decided not to make an effort to remove them.
(7) A network of massive walls was built and soil fill was deposited between them. The ‘eastern wall’ was built very close to the northern corner of the drainage channel where the fallen voussoirs are located.
(8) The construction of the arch was completed.
(9) The area along the Western Wall and where the paved street and shops were built was straightened and leveled.