JERUSALEM, June 21 (Reuters/Alastair Macdonald) - With one last exit stamp in my passport, I end a three-year reporting assignment in the Holy Land that has been marked by images of frontiers, by a sense of walls going up and fewer and fewer people finding a way through.

From the minefields of Israel's front lines with Syria and Lebanon to the fortified fences around the West Bank and Gaza Strip -- much in this month's headlines -- to the walls, old and new, of Jerusalem, physical barriers shape the lives of the 12 million people cut off here in what was once called Palestine.

But those lives, and millions more touched by events that reach far beyond these borders, are marked, too, by less visible internal frontiers -- religious, cultural, ethnic, political.

What has struck me is seeing people locked in, and locked out, by a spreading labyrinth of boundaries and parallel worlds, all in an area just a third the size of my native Scotland.

As a Reuters correspondent, I'm used to explaining what I see to people living a world away. In Israel and the Palestinian territories, I'm as often asked to describe lives being led only a few miles down the road, to neighbours who no longer meet.

Is it true their women can't go out in public now? an Israeli soldier asked me over cappuccino at a shopping mall just outside the Gaza Strip after Hamas Islamists seized the enclave.

The answer was 'no'. But the questions can be just as naive from Palestinians about an Israel many once knew quite well.

As a foreigner and a journalist, I've had special privileges to cross these frontiers, whether the daunting maze and cages of Gaza's Erez Terminal or the once-walled, now invisible but still palpable, Green Line from Jerusalem's Arab east to Jewish west.

Most locals cannot, or do not, make such journeys.

Between Gaza and Israel, foreign journalists join just a few dozen aid workers each day and Palestinians heading to Israeli hospitals on a half-mile (700-meter) trek across no man's land.

Normally, these days, it's a peaceful place, teeming with wildlife, a brief buffer zone between Gaza, an Arab city going backwards on donkey carts and embargoed scarcities, and the neat farms, hi-tech factories and shopping malls of southern Israel.

ADRIFT IN THE MIDDLE EAST

But Gaza is not the only island in this landlocked chain.

Israel is essentially cut off too. I've stood on its borders with Lebanon and Syria, where mines and tanks and trenches mark front lines that are still on alert. I've crossed its little-used transit points to Jordan and Egypt, signatories to a cold peace.

From Israeli bases on the Golan Heights you can make out the lights of Damascus. From Jerusalem, the Jordanian capital Amman glows across the valley. Israel sits adrift from both.

I've watched the estrangement between Palestinians of rival political camps leave Gaza and the West Bank virtually at war.

I've seen Israelis grapple with divisions among themselves too -- between descendants of early European immigrants and later arrivals from the Middle East, Ethiopia and the Soviet Union.

Ultra-Orthodox boys hauling barriers around their expanding neighbourhoods in Jerusalem to protect their Sabbath observances from intrusion by secular Jews has also been a potent image.

Inside the Old City's gates, Ottoman-era Quarters -- Muslim, Jewish, Christian and Armenian -- map communal rivalries still alive today. Small battlefields marked by razor wire, flags and hurled garbage show where Israelis are settling in Arab areas.

As communities turn their backs on each other, I've seen the city's trilingual street signs defaced: Arabic is blacked out in the west, Hebrew erased in the east. (The English is ignored.)

I've also watched smaller groups like the Christian Arabs slugging it out in turf wars, in the church around Jesus's tomb.

WALLING OFF MEMORIES

The most visible wall is the new one that snakes around greater Jerusalem -- protecting it, Israel says, from suicide bombers while cutting them off from their families, according to Palestinians.

I've found myself describing to colleagues in Ramallah, just a 15-minute drive away for me, how the scenery of their native Jerusalem is changing. Like Israelis who reminisce to me fondly about trips to beachfront seafood restaurants in Gaza, for many Palestinians Jerusalem exists now in the mists of memory alone.

They complain, too, that the barrier penning them into the West Bank is a frontier in one direction only. Half a million Israelis live there, in an archipelago of hilltop settlements, their red, pitched roofs an image of contrast to Arab villages.

Other partitions and parallels abound. In Hebron, the shrine of Abraham, patriarch of both faiths, is divided into Jewish and Muslim sections, though that has not prevented bloodshed.

Many argue all this wall-building is the only way to contain violence, though geography and demography hardly make it simple.

Yet there are images that stay with me of those who reach over the walls. I've seen it in the Reuters journalists I worked with. Their professionalism is blind to being Palestinian or Israeli, even if partisan critics from all sides question that.

But as borders have closed, ordinary folk who shake hands across them can find themselves shunned by their own community.

Professional collaborations have grown rarer, too. I've seen it, still, in Israeli hospitals, where injuries and violence to colleagues have taken me. Staff and patients of all communities mingle easily, an extraordinary contrast to the world outside.

So it's probably no coincidence it was a Gaza doctor, fluent in Hebrew, who inspired a rare outbreak of empathy across the frontiers last year, when Israeli television aired his plea for help after his children were killed during Israel's offensive.

Sympathy for him among many Israelis and the doctor's own dignified refusal to bear grudges stood out for me, though they hardly began to offset bitterness the war left on either side.

As I leave, passing yet another frontier checkpoint for a final time, I see little sign of any of these walls coming down.