"In the name of God," said the form we had to fill in to get a press card. Was it "in the name of God" that we had to shroud ourselves in loose clothes and headscarves, the minute our plane landed on Iranian soil? Was it "in the name of God" that nearly all the women we saw, as we crawled through the rush-hour traffic from Tehran airport, were wearing black? And it's in the name of God, presumably, that Sakineh Mohammadi Ashtiani has, for the past five years, been living under the threat of being stoned to death.
It was certainly "in the name of God" that Ayatollah Khomenei, whose massive mausoleum you pass on the way from the airport, spearheaded the revolution that turned Iran from a police state headed by a corrupt Shah to a police state headed by an Islamist cleric. Started in 1989, the mausoleum still isn't finished. Perhaps it's a metaphor. This task, this attempt to bury a country, and its history, and its exquisite art and architecture and poetry and life, in a black veil of bullying fundamentalism, will never finish. You can't hide the spirit of Iran, and of the ancient civilisation of Persia, any more than you can hide the beauty of so many Iranian women.
And beauty, it's clear, even among the dreary tower blocks in the suburbs of Tehran, is important. It's clear in the flowers on a roundabout, in a sudden, brilliantly coloured mural on the side of a concrete apartment block, and, weirdly, in the large number of bandages on faces. These, our guide told us, were for nose jobs. Thousands of Iranians have nose jobs. Some of the people sporting bandages hadn't even had them. A nose job was a status symbol, and a bandage was better than nothing. We were beginning to get the message. This is a complicated culture in which all is not as it seems.
Our first stop was Tehran's National Archeological Museum. Here you get a dizzying sense of the layers of civilisation and history that make most countries in the world feel like gawky adolescents. There's pottery dating back to 7000 BC – yes, that's 90 centuries ago – and an extraordinary range of ceramics, painted, and sometimes carved, with scorpions, snakes and fish.
Around the corner, on a Sumerian tablet from the fourth millennium BC, there's some of the oldest writing in the world. And around another one, there's one of the oldest wheels in the world. This litany of cultural milestones almost gets boring, but then, among the luxuriant beards on the stone statues from the first Persian empire, you stumble upon a mass of curly, real hair. A real beard, on a real head, with real eyebrows. This is Saltman, discovered by Iranian miners in 1993 and apparently 1,700 years old. Denis Healey, eat your heart out.
There were no curly beards at the Crown Jewels, next door. Instead, there was a neat little moustache on the face of the fierce guide, who marched us round at dizzying speed. His commentary on the gaudy baubles in glass cases – largely royal bling passed from one bored monarch to another – barely allowed pause for breath, but his barbed references to Queen Victoria and her scions were a salutary reminder that Iranians have no reason to love the Brits. For the sake of brevity, let's just say oil (again). It was our love of the sticky stuff that had us installing (with the help of the CIA) a regime that led to the mass terror that led to the near-nightmare of now. Perhaps it's just as well that Iranians are adept at something they call ta'arof, a form of ritual politeness that allows the appearance of good manners without revealing the true feelings behind them.
"The people of Shiraz are very mellow," our guide told us the next morning, as we landed at Shiraz airport, swapping the smog of Tehran for a brilliant blue sky. It was hard to hear the words "Shiraz" and "mellow" and not think about a glass of the stuff, but we were trying, we were really trying, not to think about wine. "We used to do our praying in private and our partying in public" said our guide, "but now it's the other way round". The truth, of course, is that in the comfort of their own homes, many Iranians drink fine wines and wear mini-skirts. But we were not Iranians and we were not in people's homes.
In the Eram gardens, however, we felt as though we were in somebody's home, or at least their garden. Women smiled and waved. Older women in chadors inched up to us and stared, schoolgirls giggled and a group of younger women – extremely glamorous, with bright lipstick, eyes heavy with mascara, and highlighted fringes poking out from their veils like the crest on a cockatoo – chatted to us in excellent English.
We had our own guide, but were repeatedly overwhelmed (and sometimes slowed down) by the polite curiosity of strangers. It's one of the many ironies of this complicated country that a nation with an international reputation for hostility should be inhabited by a people of such rare, and hospitable, charm.
It was Cyrus, that great Persian hero, who in 500BC created a garden in Pasadi. He brought trees and flowers from all over his empire and then started to build palaces in the garden. "Eram", our guide told us, means "heaven". And there was something profoundly soothing, and beautiful, about the tranquil pools, the cypress trees, the rows of roses and the heady scent of orange trees. You can see why young couples meet in parks to pretend to study, but really to talk, flirt and maybe even read each other poetry.
The real religion of Iran, it's tempting to say, is poetry. At the tomb of Hafiz, the great 14th-century Shirazi poet, we saw people kissing the white marble and reciting his poems, about love and the beloved, as if their life depended on it, as if beneath that marble was the beloved they had lost. Iranians revere the work of Hafiz. They all recite him, turn to him for guidance and speak – but if our guide is anything to go by, it sounds like singing – of the rose, and the nightingale and, yes, the wine that they may not, at least in public, drink.
"The one good thing the Shah did," said our guide the next morning, "was to reintroduce Persia to the world, and explain that we are not Arabs." We were on the outskirts of Persepolis, next to the tent city which the Shah of Iran erected as accommodation for world leaders (at a cost of $20m) for a massive party in 1971 to show off the splendours of his country to the world, and celebrate 2,500 years of the Persian empire.
Only the ghosts of the tents remain, but of the palace complex, built by Darius the Great in 515BC, there's still a breathtaking array of treasures. The scale of it – more than 13 hectares – is astonishing. But then it was, until it was burnt to the ground by Alexander the Great in 330BC, the key ceremonial palace for the Persian Empire. It was here that princes and leaders came to pay homage to the Persian king, or at least to pretend to.
In amazingly well-preserved bas reliefs, you can see them: Scythians in pointy hats, Indians wearing skirt wraps, Parthians leading a camel – all smiling, because they're here to mark the Persian New Year, which is also the first day of spring. You could spend days wandering round the site, gazing at columns and statues, and imagining what it would be like if it wasn't all white stone, but rich colours, burnished with lapis lazuli, turquoise and gold. We, alas, had only hours.
From Persepolis, we went to Nagsh-e-Rostam, where the Achaemenid kings – Darius the Great, Xerxes or Xerxes II and Darius II – are buried. The tombs are carved out of the rocks, and on V C them are Sassanid reliefs and inscriptions, including one inviting passers-by to ponder "how many are the countries which King Darius held". No wonder Iranians have dreams of greater grandeur. A couple of hours away, on a windswept plain, you can see where it all, or at least quite a lot of it, started. Cyrus the Great built Pasargadae as a memorial to his victory over the Medes in 550BC. It's a thrill to see the tomb of the man whose cuneiform cylinder, which you can see in the British Museum, is widely regarded as the first human-rights charter.
Pretty much nothing can prepare you for the thrill of Esfahan, though the six-hour drive from Pasargadae gives you time to think about it. The hotel was gorgeous enough. Hotels in Iran tend to have a slightly Seventies Soviet flavour, but the Hotel Abbasi, restored from an 18th-century caravanserai, and modelled on the palaces of Shah Abbas, felt like a glimpse of another world. There were more glimpses of it in our sightseeing the next day: in the lovely Khaju Bridge, built by Shah Abbas II in 1650, where courting couples have picnics; in the Vank Cathedral, built for Armenian Christians and full of fabulous frescos; in the Chehel Sutun pavilion, set in beautiful gardens and studded with fine paintings and, most of all, in the vast central square, and the buildings around it.
The Imam Square, as it's now known, is three times the size of St Mark's Square and smaller only than Tiananmen. When you're in it, you can see why someone might once have suggested that "Esfahan is half the world". When you sit in a café gazing out at the fountains in the square, or when you wander round the Ali Qapu palace, or when you look up at the domed ceiling of the Masjid-I Imam, you feel as if it's half the world and also a glimpse of heaven.
"Whatever is with you will be exhausted," said one of the street signs designed to whip up Islamic fervour. Certainly, there's enough to see in Iran to tire you out. But what you do see, in architecture, and art, and gardens, and in the impeccable manners of a people who keep smiling against considerable odds, is almost enough to make you agree with the second part of the slogan: "Whatever is with Allah will last."
Travel essentials: Iran
* The writer travelled with Cox & Kings (020-7873 5000; coxandkings.co.uk) which offers escorted and private travel in Iran. "Treasures of Iran" is a nine-day group tour priced from £1,795 per person, including Heathrow-Tehran flights with BMI, escorted transfers, excursions and half board accommodation.
* British passport-holders need a visa to visit Iran. They can be obtained from the Iranian Consulate at 50 Kensington Court, London W8 5DB (020-7937 5225; iran-embassy.org.uk; fee £68). Be warned that, according to the Foreign Office ( fco.gov.uk), the application process can be "protracted and unpredictable". It further warns that "Since 9 February 2010, British applicants have been required to provide fingerprints when applying for an Iranian entry visa. Women, and girls over the age of nine, should wear a headscarf in their application photos."
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