Pool of Siloam

The Pool of Siloam (, , "Breikhat HaShiloah") (), is a rock-cut pool on the southern slope of the City of David / Wadi Hilweh, considered by some archaeologists to be the original site of Jerusalem, located outside the walls of the Old City to the southeast. The pool was fed by the waters of the Gihon Spring, carried there by the Siloam Tunnel.
History.
During the Second Temple period, the Pool of Siloam was centrally located in the Jerusalem suburb of Acra (), also known as the Lower City.
Today, the Pool of Siloam is the lowest place in altitude within the historical city of Jerusalem, with an elevation of about above sea level. The ascent from it unto the Temple Mount meant a gain of in altitude at a linear distance of about , with a mean elevation in the Temple Mount of above sea level. According to the Jerusalem Talmud ("Hagigah"), the Pool of Siloam was the starting point for pilgrims who made the annual pilgrimage to Jerusalem, and where they ascended by foot to the inner court of the Temple Mount to bring their sacrificial offerings. 
Hezekiah.
The Pool of Siloam was built during the reign of Hezekiah (715–687/6 BCE), to leave besieging armies without access to the spring's waters. The pool was fed by the newly constructed Siloam tunnel. An older Canaanite tunnel had been very vulnerable to attackers, so, under threat from the Assyrian king Sennacherib, Hezekiah sealed up the old outlet of the Gihon Spring and built the new underground Siloam tunnel in place of the older tunnel (). 
During this period the Pool of Siloam was sometimes known as the Lower Pool (), as opposed to a more ancient Upper Pool (, ) formerly fed by the older Canannite tunnel.
Second Temple period.
The pool was reconstructed no earlier than the reign of Alexander Jannaeus (103-76 BCE), although it is not clear whether this pool was in the same location as the earlier pool built by Hezekiah — if so, all traces of the earlier construction have been destroyed. The pool remained in use during the time of Jesus. According to the Gospel of John, Jesus sent "a man blind from birth" to the pool in order to complete his healing. As a freshwater reservoir, the pool would have been a major gathering place for ancient Jews making religious pilgrimages to the city. Some scholars, influenced by Jesus commanding the blind man to wash in the pool, suggest that it was probably used as a mikvah (ritual bath). However, mikvahs are usually much smaller in size, and if the pool were a mikvah, it would be the largest ever found by a substantial margin. Yoel Elitzur has proposed that the pool was used for swimming rather than ritual immersion.
The pool was destroyed and covered after the First Jewish–Roman War in the year 70. Dating was indicated by a number of coins discovered on the stones of the patio near the pool to the north, all from the days of the Great Revolt. The latest coin is dated with "4 years to the day of the Great Revolt", meaning the year 69. In the years following the destruction, winter rains washed alluvium from the hills down to the valley and down the slopes of Mount Zion to the west of the pool; the pool was filled with silt layers (up to 4 m in some places) until it was covered completely.
Late Roman and Byzantine periods.
Roman sources mention a "Shrine of the Four Nymphs" ("Tetranymphon"), a nymphaeum built by Hadrian during the construction of Aelia Capitolina in 135 and mentioned in Byzantine works such as the 7th-century "Chronicon Paschale"; other nymphaea built by Hadrian, such as that at Sagalassos, are very similar. It is unlikely that this shrine was built on the site of the Second Temple Pool of Siloam, but it may have been a precursor to the Byzantine reconstruction.
In the 5th century, a pool was constructed at the end of the Siloam Tunnel, at the behest of the Empress of the Byzantine Empire, Aelia Eudocia. This pool survives to the present day, surrounded on all sides by a high stone wall with an arched entrance to Hezekiah's Tunnel. This pool is around 70 yards from the Second Temple (or Lower) Pool of Siloam, and is significantly smaller. Until the discovery of the Second Temple pool, this pool was wrongly thought to be the one described in the New Testament and Second Temple sources.
Discovery in the 21st century.
The pool was rediscovered during an excavation work for a sewer in the autumn of 2004, by Ir David Foundation workers, following a request and directions given by archaeologists Eli Shukron accompanied by Ori Orbach from the Israel Nature and Parks Authority. Archaeologists Eli Shukron and Ronny Reich (working with the Israel Antiquities Authority) uncovered stone steps, and it became obvious that these steps were likely to have been part of the Second Temple period pool. Excavations commenced and confirmed the initial supposition; the find was formally announced on August 9, 2005, and received substantial international media attention. The excavations also revealed that the pool was 225 feet wide, and that steps existed on at least three sides of the pool. A portion of this pool remains unexcavated, as the land above it is owned by a nearby Greek Orthodox church and is occupied by an orchard known as the King's Garden (compare ). The pool is not perfectly rectangular, but a soft trapezoid. There are three sets of five steps, two leading to a platform, before the bottom is reached, and it has been suggested that the steps were designed to accommodate various water levels. The pool is stone-lined, but underneath, there is evidence of an earlier version that was merely plastered (to help it retain water). Coins from the reign of Alexander Jannaeus were found embedded in the plaster lining of the pool, and therefore provide a secure earliest date for the pool's (re-)construction.
Archaeologists excavating the site around the Pool of Siloam in the 1880s have noted that there was a stairway of 34 rock-hewn steps to the west of the Pool of Siloam leading up from a court in front of the Pool of Siloam. The breadth of the steps varies from 27 feet at the top to 22 feet at the bottom.