When George W. Bush visits Israel next week, he's reportedly planning to take time off for a visit to the ruins of Capernaum on the Sea of Galilee, where Jesus is said to have lived and preached. I shouldn't begrudge someone shlepping across the world a couple hours for a private pilgrimage. But if Bush wants to pry time free from meetings in Jerusalem, it would be better spent on a tour of the Israeli separation barrier, a.k.a. fence, a.k.a. wall. Plenty of human rights activists who speak good English (maybe too good for W.) would be happy to guide him. The trip could give him a visceral feeling for why he should finally devote himself seriously to an Israeli-Palestinian agreement, instead of just dabbling.

Realistically, the president is no more likely to head out to the fence than a visiting CEO looking over a company is likely to talk to the shop-floor workers who know how the place really runs. So let me describe a bit of what he'll miss, and what it means.

A good stop would be the Palestinian village of Azzun Atma, in the foothills on the very western edge of the West Bank. The barrier -- actually a 200-foot-wide strip of barbed wire, patrol roads, and electronic sensors -- twists through the hills to divide the small farming village from the suburban Israeli settlements on either side of it. (Check this map from the B'Tselem human rights group.) As a result, the suburbs have free access to Israel. Azzun Atma is completely enclosed; an Israeli army checkpoint stands on the one road out to the rest of the West Bank. It's shut between 10 p.m. and 6 a.m., says Abdulkarim Ayoub Ahmed, secretary of the village council. I called Ahmed to confirm a recent report on the Israeli Ynet news site that women near the end of pregnancy prefer to leave the village and stay with relatives elsewhere, for fear they'll go into labor at night. It's true, he said. The village has 60-70 births a year, and more than half the women leave in advance. In December, a woman who hadn't left in advance gave birth in her car at the closed checkpoint at night.

Nearly five years ago, when construction of the fence had just begun, Ahmed told me that it would "destroy our lives." Col. Dany Tirza, the man who was planning the precise route of the barrier, insisted it would hardly inconvenience the people of Azzun Atma. They'd have to drive more kilometers to get to the nearest Palestinian town, Qalqilya. But it would take less time, he said, because once the barrier was protecting Israel from terrorists, the army would be able to remove roadblocks that restrict Palestinian travel within the West Bank.

Tirza carried a high-security laptop on which he could call up aerial photos of the West Bank, with overlays showing the route he was designing. Pregnant women needing to get to the hospital at night did not appear. Tirza's laptop symbolized the techno-military hubris of the fence project, as conceived by then-prime minister Ariel Sharon: Engineering would stop terror.

Let me stress: Stopping terror -- despite the way that both Sharon and Bush exploited the idea -- was a reasonable goal. In 2003, deciding to take a bus or sit in a café in Israel was an existential choice; it made you think about whether you'd see your children again. Many Israeli leftists favored building a fence on the Green Line, the border between Israel and the West Bank, as an impediment to suicide bombers. An added political benefit was that it would show Israelis where occupied territory began, and imply an eventual pullback to that line in a peace agreement.

For just that reason, Sharon initially opposed a fence. When he adopted the idea, he and Tirza worked together on a route that zigzagged into the West Bank, far from the Green Line, to put as many settlements as possible on the Israeli side. This was Sharon's counter-statement of where a border should run. Tirza told me that the Palestinians the route he was drawing would become the "reference line" for an agreed border. I have yet to meet any Palestinians who agree with that.

Political and legal battles have led to changes in the route since then. As now planned, the fence will be 723 kilometers long, more than twice the length of the Green Line. Defense Ministry spokesman Shlomo Dror told me this week that 60 percent has been built so far. From that, you might calculate that a fence along the Green Line would already be done. But length isn't the only problem. The military wanted a perfect fence; it heaped on requirements -- the sensors, the cameras, the roads -- in the standard way that defense projects get inflated. The Defense Ministry and Finance Ministry squabble over funding. Dror said the target date for completion is now 2010.

So Bush could also visit the areas where nothing has yet been built: bits near Jerusalem, or a long stretch in the hills south of Hebron. According to Dror, the holes are the reasons that Israel still needs to maintain roadblocks throughout the West Bank: They make it far more difficult for a would-be suicide bomber from Nablus to reach the gap in the fence in Jerusalem and sneak into Israel.

The reality is messier, though. The barrier is probably part of the reason that bombings inside Israel have virtually ended. Improved Israeli intelligence is another. But the change in Palestinian political atmosphere is also a factor: Out of despair or political realism, at least some of the Palestinian groups that once sent bombers have apparently stopped. On the other hand, even if the fence were completed this week, the army would not want to take down roadblocks. It would be worried about Hamas or Islamic Jihad overcoming the West Bank fence the same way they keep up the struggle from Gaza -- with cheap missiles -- and it would want to keep a tight grip on the territory.

There's another reason for Bush to look at the fence in Jerusalem, because this is where the original conception breaks down completely, even the left's version. There's no way to build a barrier along the Green Line in the city. Too many Jewish neighborhoods have been built beyond the line. Too many Palestinians work on the Israeli side. Yet leaving a hole in the fence in Jerusalem would vitiate the whole project.

Instead, Israel has built the fence around annexed East Jerusalem -- dividing Palestinians in the West Bank from their urban center, another social and political disaster. In a few places, the fence cuts through Palestinian parts of the city. Since Jerusalem Palestinians are legally residents of Israel, some take the logical step and move inside the fence, where rents have risen in Palestinian neighborhoods. (The market has begun pushing Palestinians to rent in Pisgat Ze'ev, a post-1967 Jewish neighborhood beyond the Green Line at the north end of the city. Integrating Pisgat Ze'ev certainly wasn't what Tirza and Sharon had in mind when they planned the barrier route.) Politically, as I've written before, Jerusalem will have to be divided. Physically, there's no longer any logical place to put a fence.

In the end, the fence has shown the failure of techno-military thinking. In the short run, it has probably served as an impediment to terrorists, but an impediment is not a solution. At the same time, it has deepened the bitterness that feeds the violence. It is a Band-Aid over an abscess. No one seriously suggests that Israel would be significantly safer today pulling back unilaterally in the West Bank than it would have been before construction of the barrier began. A tour of the barrier would make clear that the only realistic solution to the conflict is political. But that pilgrimage is not on Bush's itinerary.