Archaeologists in Jerusalem say they have found an underground drainage channel that was used by Jews to escape from the Romans in 70 AD.
Archaeologists think the tunnel leads to the Kidron River
The channel was buried under the rubble of the Second Temple, which was destroyed by Roman conquerors in the Siege of Jerusalem.
Scores of people are thought to have sheltered and lived in the tunnel until they were able to flee the city.
Several parts of the tunnel have been preserved intact.
The tunnel is believed to have been Jerusalem's main drainage channel at the time of the Roman conquest, stretching beneath the city and eventually reaching the Dead Sea, the Israel Antiquities Authority said in a statement.
"The channel... is covered with heavy stone slabs that are actually the paving stones of the street.
"In some places the channel reaches a height of about three metres and is one metre wide, so that it is possible to walk in it comfortably," the statement said.
Eli Shukron of the Antiquities Authority said: "It was a place where people hid and fled to from burning, destroyed Jerusalem."
Mr Shukron said excavators looking for Jerusalem's main road from the time of the Second Temple happened to find a small drainage channel. That led them to the larger tunnel beneath the road.
JERUSALEM HOLY SITE
SACRED TO JEWS: Site of first and second Temples and the rock on which Abraham offered his son as a sacrifice. As the visible remnant of the Temple, the Western Wall is the holiest site in Judaism
SACRED TO MUSLIMS: First direction of prayer for Muslims, site of Prophet Muhammad's ascent into, home to al-Aqsa mosque and Dome of the Rock
Pottery shards and coins from the end of the Second Temple period were also discovered inside the tunnel.
About 100 metres of tunnel has been excavated so far, stretching north from the Shiloah Pool at the Old City's southern end to about 10 metres west of the Western Wall (the so-called Wailing Wall), which is all that is left of the Second Temple.
Archaeologists think the tunnel leads to the Kidron River, which empties into the Dead Sea.
The destruction of the Second Temple is still mourned annually on the Jewish fast Tisha B'Av.
The Temple Mount or Haram al-Sharif (Noble Sanctuary) is the holiest site in Judaism and Islam's third holiest shrine.