Inside the dim underground passage, the air is cool and heavy with the dust of two millenniums. A man named Amnon points out a doorway-sized mysterious wet spot along the Western Wall tunnel. These immense, dripping stones are underneath the Temple Mount, though not directly below the Al-Aqsa mosque, which is precious to Islam as the place of Muhammad's ascension. Attention to that proximity set off fighting that has killed 67 people in less than a week and plunged the Middle East peace process into a state of crisis and conflict.
Here, archaeology is war. Or at least, the documentation of wars past, in their most tangible form.
And it is why the opening of the Western Wall tunnel sent a staggering blow to Israeli-Palestinian relations, serving as a historical reminder that archaeology can easily provide a spark for wars to come.
To Israelis, the tunnel was extended to give visitors a better concept of the massive scope of the Second Temple, of which only the Western Wall remains exposed. It is the holiest site in Judaism. But Palestinians worry the additional excavations could shake the foundations of the sacred Dome of the Rock and the Al-Aqsa Mosque, which lie somewhere overhead.
For Prime Minister Benjamin Netanyahu, to close the tunnel at Palestinian insistence would be to be cede some of Israel's sovereignty over Jerusalem, which he views as the country's eternal, indivisible capital. Likewise, for Palestinians the tunnel is an example of Israel tightening its grip over East Jerusalem, which Palestinians want as a capital of a future state. The matter is to be settled in yet-unscheduled "final status" talks, in which the explosive issue of Jerusalem will be discussed last.
But when the remnants and future of this cradle of monotheism are at stake, the status of Jerusalem does not want to wait, and archaeology is a cause for war.
The Hasmonean tunnel that Israel opened last week is actually a water passage that served as the main source for cisterns on the Temple Mount during the Herodian period, named for the Jews' King Herod who ruled between 37 and 4 BC. After the Romans sacked Jerusalem, others later built over the ruins.
The Israelis have been digging and removing dirt from the tunnel for 12 years. In the 1980s, excavations caused cracking in a building in the Muslim quarter of the old city, which is overhead.
For some Arabs, the mere memory of that - and the fact that an extremist Jewish group was caught plotting to blow up the mosques - is enough to arouse suspicion about the recent digging. To Palestinian archaeologists, there is no proof, however, that the tunnel dates to the Hasmonean/Jewish period.
Orthodox Jewish belief holds that when the Messiah comes a temple will be rebuilt on the spot of the current Muslim shrines.
There is much confusion about whether the tunnel runs under the Dome of the Rock. Israel insists it does not, but runs near it along the Western Wall. Palestinians suspect it runs underneath, or that additional tunnels do.
Jews are adamant: "This is part of the original Herodian street," the Israeli guide says, "the same street Jesus walked in 2000 years ago. We're in a time tunnel."
Israel says the tunneling allows more tourists to pass through. Only 400 tourists used to be able to pass through each day. Now, Israel expects to bring in 1,500 per day - and $5,000 per day in visitor fees.
At root of the discord is not just religion, but who has greater historical claim to the land. Each of the two has gone to great pains to show who was there first. This year, for example, Palestinians boycotted Israel's celebration of the 3,000th anniversary of Jerusalem, saying it was a Judeo-centric view of the holy city.
Increasingly, Palestinians describe themselves as the descendants of Canaanites, who preceded Israelites in the area according to the Bible. Their Israeli critics say that this gives them more leverage than Islam, which is only 1,400 years old.
Israel says it won't close the tunnel. Says Mr. Netanyahu: "We are literally touching the bedrock of our existence."