By Matthew Price
BBC News, in Jerusalem
Every day the number 163 bus drives through the orthodox neighbourhoods of Jewish West Jerusalem.
Palestinians say the barrier risks ending co-existence between Arabs and Jews
It heads for Bethlehem in the West Bank. The journey takes about 40 minutes, skirting Arab-dominated East Jerusalem which Israel has occupied since 1967.
By the time the 163 reaches the checkpoint into Bethlehem the bus is full of Jewish worshippers. The men in black coats and hats, the women in long skirts.
And then the bus arrives at its destination. One of Judaism's holiest sites: Rachel's Tomb. For centuries it has been a part of Bethlehem, but soon it will lie outside the town.
Israel is building its wall here, an eight metre high, grey concrete edifice now dominates the new de facto boundary between Jerusalem and Bethlehem.
Soon the wall will curl around Rachel's Tomb, making it part of the Jerusalem district.
The land nearby, olive groves which once ran up to Bethlehem's houses, will also be separated from the town.
For anyone who knows this area well, the change over the last few months has been dramatic.
In many ways it no longer matters where the lines are drawn on maps. What matters increasingly are the concrete facts on the ground.
Even from the centre of West Jerusalem the effect is undeniable.
Look to the horizon, and you'll see the wall.
It's defining what Jerusalem is. And the land around it.
That concerns Zaed Abu Ziad, a Palestinian member of parliament for East Jerusalem. But now he lives on the wrong side of the wall.
"I was elected in 1996 by the Arabs of East Jerusalem to represent them in our parliament," he tells me. "I am not allowed to see the people of my constituency. If I go to East Jerusalem I am arrested."
I ask how he feels when he sees the changes going on around Jerusalem.
"Well I feel scared for the future. Because what the Israelis are doing now in the city is a time bomb which will explode any time in the future.
"They are undermining any possibility for co-existence between Arabs and Jews in the city and even in the region."
It is a stark warning.
Both Israelis and Palestinians claim Jerusalem as their capital.
The Palestinians say east Jerusalem including the Old City will be the capital of their future state.
Israel says the city will remain undivided. By that it means both Jewish west Jerusalem and the east - which is mostly inhabited by Palestinians - will be inside the future final borders of Israel.
And to make sure that happens some Israelis are taking things into their own hands.
Uri Bank, one of the Jewish leaders of a developing real estate battle showed me round the lanes north of the Old City in east Jerusalem.
"We have four families who live here in a small enclave, amongst all these Arabs and Palestinians in east Jerusalem.
"And I really think this is the forefront of Zionism today, realising that there is a land war going on.
"And whoever wins that land war, Jews or Arabs, is going to be able to take control of the eastern side of the city.
"We're trying to tempt them into letting us buy their real estate.
"On the ground Palestinians do have a majority in east Jerusalem. If we want to lay claim to these areas not only on the sovereign level but also on the ground we have to have families living in dots through all of east Jerusalem.
"Dots which we will try to connect later on."
But this is not just about buying houses in East Jerusalem. There is also a wider Israeli government plan which could permanently change Jerusalem.
On a hill above the city I met up with Dr Menachem Klein. A left wing Israeli who has spent much of his life trying to resolve the competing claims to Jerusalem.
He has worked with a number of Israeli prime ministers.
In front of us lay the West Bank - mostly rural agricultural land. In the distance the settlement of Maale Adumin. Below Palestinian farmers working the same land they have for generations.
It is here that the Israeli Prime Minister Ariel Sharon plans to build thousands of homes, connecting Maale Adumin to Jerusalem.
Pointing down into the valley below Menachem Klein told me: "This is the area that Israel hopes to annex to Jerusalem, to become greater Jerusalem.
"Sharon's strategic plan is to regain Israeli control over Arab east Jerusalem, by disconnecting Arab east Jerusalem from its hinterland in the West Bank."
Indeed after a meeting with President Bush earlier this month Mr Sharon himself told reporters: "Of course, we are very much interested that there will be contiguity between Maale Adumin and Jerusalem."
Palestinians fear that could make it almost impossible for them one day to have east Jerusalem as the capital of their future state.
But the Israeli foreign ministry spokesman Mark Regev denies this.
"You know, according to the Road Map Jerusalem is a final status issue that will be dealt with when we get to that third and final stage of the Road Map."
But, I put it to him, aren't the events on the ground pre-empting that final status?
"We don't believe so," he told me. "We're hopeful that it's possible in the future to reach understandings, agreements with the Palestinians about all the final status issues including Jerusalem.
"We have our position. We'll bring that to the table. Palestinians will bring their positions to the table."
But, I asked, how can the Palestinians possibly still hope to have east Jerusalem as their future capital if Israel has already sealed it off from the West Bank?
"I think what we're doing does not in anyway undermine the possibility of the creation of an independent Palestinian state."
That may or may not turn out to be true. The changes to the geography of Jerusalem may well not be permanent.
But when you see this city changing shape by the day, you do wonder whether sometime, sooner or later, there will be nothing left to negotiate.