The Pope will today venture into the scalding inner core of the three-way religious conflict that has spawned divisions in the city of Jerusalem for 2,000 years, in a precarious but dramatic finale to his six-day Middle East pilgrimage.
The frail Pontiff will journey to the holy city's biggest fault line where theological rivalries and contemporary nationalist conflicts fuse. He is going to the Temple Mount or, as it is known to Muslims, Haram al-Sharif, and the nearby Wailing Wall, Judaism's most sacred site.
Temple Mount is the scene of the best-known, real estate battle in history. For Islam, the Haram al-Sharif, their third holiest shrine which includes the Dome on the Rock, is the launching pad from which Mohammed sprang on his horse to the heaven. But Jews (and some Christians) believe it is the site of the Second Temple. The faithful are committed to securing its return.
In 1990, Israeli police shot 18 Arabs, rioting after a rumour swept through that religious fanatics were trying to encroach on their hallowed turf. Six years later, 80 people died in unrest which followed an Israeli decision to open a tunnel near the site.
The Haram al-Sharif lies in Jerusalem's Old City, at the centre of one of the biggest bones of contention in the peace talks. To Israeli irritation, the Palestinians threatened to fly their flag when the Pope arrives to meet the Great Mufti of Jerusalem this morning.
They want to underscore their view that the place symbolises their struggle to create a capital in Arab east Jerusalem, occupied by Israel in 1967 and annexed in contravention of international law.
The Israelis this week bad-temperedly reminded the world that they will be in charge of supervising the papal excursion into the Old City (except on the Haram itself), in line with the Jewish goal of making Jerusalem Israel's unified and eternal capital.
John Paul II does not enter this vipers' nest as an uninterested party. Jerusalem, dotted with New Testament sites, lies at the heart of the Christian faith, just as it does for the two competing monotheistic religions. The Vatican emphasised this last month by signing an agreement with the Palestinian leader Yasser Arafat showing it would oppose Israeli attempts to impose unilateral decisions on the city's future.
There are 180,000 Christians in Israel and the occupied territories, mostly Arabs, including six Catholic churches: Latin, Melkites, Maronites, Syrians, Chaldean and Armenian. And there are hundreds of thousands of pilgrims and tourists who visit Israel. The Vatican wants to ensure Christian control of the sacred - and lucrative - assets which draw them in.
Today the Pope will preside over a mass at the jewel in the crown of the holy sites, the Church of the Holy Sepulchre, where the crucifixion is supposed to have happened.
He will preach the need for peace and goodwill among faiths, in this theological battlefield on three of the great montheistic faiths. But, in this fractious city, this seems doomed to fall on stony ground.