Architectural historian and broadcaster Dan Cruickshank treks into the mountains of western Afghanistan to visit and film an architectural treasure, the leaning minaret of Jam.
Herat is a wonderful city. It was rebuilt by Alexander the Great around 330 BC, and was later one of the major cities in Tamerlane's empire.
Herat's ancient buildings have been damaged in many military conflicts
We had come not to enjoy its glories, but to get our permission to travel validated by local officials.
First we went to see the Deputy Governor of Herat. Haji Mir Abdul Khaliq was a mujahideen in the 1980s and - robed, turbaned and bearded - looked a formidable character. He was delighted that we wanted to go to Jam.
"Our history is a source of great national pride," he told us. "It's good you should see one of our greatest buildings and show the world."
The Chief of Police wanted to offer us protection, not that we really needed it, he said, more as a courtesy.
He suggested a dozen armed police.
But when we went to see the senior police chief of all the provinces of western Afghanistan, he increased our protection to 60 men. And to fool enemies, he said, we must hit the road immediately.
Within an hour we were heading east from Herat, my four-wheel-drive part of a convoy of over a dozen police vehicles, most loaded with heavily armed men.
The desert landscape was punctuated by the green of fields, beside the waters of the Hari Rud river, and plantations of palms.
We passed mud-built, domed houses, with tall chimney-like wind-scoops to catch the breeze and channel it inside, to help cool the interior.
We passed the black tents of the nomadic Kushi, and their scattered flocks and wandering herds of camels seeking sustenance from the wizened scrub, which bristled amongst the broken top soil.
We wound through mountains of undulating and sculptural form - some shaded a kaleidoscope of unexpected colours - ochre, purple and red.
The few people we passed were curious - and friendly. Men waved in a sedate manner, children ran and goggled - the girls demurely pulling up their shawls to conceal their faces, while devouring us with their eyes.
Later the track-like roads stopped completely and we were travelling along riverbeds.
The 65m minaret of Jam is built entirely of baked-bricks
After many hours we turned a corner and there - between a cleft in the mountains - I saw a man-made finger of architectural perfection pointing towards the heavens.
The minaret of Jam, in its secret valley, looked magical and mysterious, almost impossibly slender and vulnerable, surrounded by the raw and rugged power of nature.
Standing 65m high, it is the most significant architectural memorial to the Ghorid empire, which in the height of its glory, in the late 12th Century, dominated Afghanistan, modern Pakistan and parts of Iran and as far south as Delhi in India.
I was amazed by the quality of the bricks and its fine surface decoration.
The lower portion carries the entire 19th sura of the Koran and tells of the Virgin Mary, Jesus Christ and of patriarchs such as Abraham and Isaac that are venerated by the three religions of The Book - Judaism, Christianity and Islam.
The minaret appears to me a reminder of the beliefs these religions have in common, and an appeal for tolerance and understanding.
But it is also emblazoned with other Koranic texts that were surely intended as a stern message to the Ghorid's Hindu enemies, who were viewed as idolatrous: "As for those who disbelieve in God... We have prepared a blazing Fire."
I crawled inside - squeezing through a small window. Then I understood how the minaret has survived so long in an earthquake region.
The walls are thick and inside is a stout brick-built central column around which not one but two staircases form a double-helix - an immensely strong form that gives the minaret some of the structural characteristics of the honeycomb.
Nearby I saw many excavations made, a local villager told me, by people looking for ancient treasures. This is tragic.
The people here, due to poverty, are being compelled to pillage their own history. And with every artefact that disappears, the history of the site becomes more difficult to unravel.
I sat and watched the sun set, the minaret casting its long shadow, like a gnomon defining a sacred precinct.
To me the minaret, leaning ominously, seemed symbolic of all historic sites in the Middle and Near East and in Central Asia, that are now threatened by conflict, looting and neglect.
It was in this part of the world, that all those things we hold to be emblems of civilisation - cities, writing, the wheel - evolved during the last 8,000 years.
This is historically the richest area of the earth, but also currently the least protected and the most vulnerable.
As I sat brooding, the minaret disappeared within the shadow of the neighbouring mountains. All was quiet, but for the barking of a dog and the harsh metallic sound of weapons being checked.
The police were settling down for a watchful night and in the morning - soon after sunrise - we would leave the minaret, alone and painfully exposed - in its beautiful and remote valley.
Dan Cruickshank's Adventures In Architecture is on BBC Two on Wednesdays at 2100BST from 2 April till 4 June. Catch up with the latest episodes at BBC iPlayer.
From Our Own Correspondent was broadcast on the BBC World Service from Saturday, 3 May, 2008. Please check the programme schedules for transmission times.