As Jerusalem has grown through the centuries, it has always reached farther for water. Most of today's supply is pumped up from the coastal plain. In antiquity, the city relied at first on the Gihon spring, which, gushing intermittently, could provide for a few thousand people. Solomon, who expanded Jerusalem to include the Temple Mount, added reservoirs in the Kidron Valley to catch and store the Gihon water. When Hezekiah built on the hill to the west, he had a pool dug to catch run-off north of the Temple. (It later became one of the Pools of Bethesda.) A hundred years later came destruction and exile. The Jews who returned in the Persian period built a rather small city. It did not grow again until the mid-2nd century, the time of the Hasmonean. This was a major expansion. The Hasmoneans would have needed more water than heretofore, and they had the technology of the aqueduct. But where was the water?

South of Jerusalem, the mountain of Judah rises gradually but steadily, a solid block, shaped like a loaf of bread. At several places along the peak (the "water divide") are springs. It was possible to lead this water by gravity into the city. Logically, the Hasmoneans would have done this, though we have no proof. Certainly Herod did. 

To see how the water problem was solved, we drive south of today's Bethlehem. East of the road are three large pools that bear the name of Solomon. In their present form, they probably date to the Mamluke period. If we go to the eastern end of the easternmost, however, we can see a green swath that winds south 300 yards. There is the spring of Etam, which takes its name from a First Testament city half a mile to the east. Herod the Great caught the spring water in two aqueducts, parts of which are still visible at various points. One of these supplied Herodion, a city he founded in the desert four miles to the east. The other followed the contours of the hills, though twice tunneling through them, for 13 miles (with a drop of less than a hundred feet) to cisterns in the Temple Mount.

Later rulers, including Pontius Pilate, took water from the peak farther south. The longest of the Roman ducts winds 25 miles (= 6 miles as the crow flies) from the springs of Ein Arrub to Solomon's Pools, thence to Jerusalem.  

The king himself rode upon a chariot in the midst of these men, who were still in armor, and had their bows fitted to them. He had on a white garment, and used to take his progress out of the city in the morning. There was a certain place about fifty furlongs distant from Jerusalem, which is called Etham, very pleasant it is in fine gardens, and abounding in rivulets of water; thither did he use to go out in the morning, sitting on high. (Antiquities  VIII 7.3)

Half a mile east of the pools is the tell of Etam. Following the water-rich valley for another half mile, we come to the village of Artas, whose name most likely derives from hortus, Latin for "garden." Here too people made a Solomonic connection, this time with the "Song of Solomon," for there (4:12) the lover compares his beloved to a "garden locked... a spring sealed up." A 17th century source explained the application to Artas: "It is called 'the sealed garden,' (because it is surrounded) not by artifice, but by nature, not by walls, but by hills and mountains." 

Source: Keel/Kuechler, pp. 727-36.