It occurs to me that I might have put my foot in it. I'm sitting in an apartment in a Tehran suburb. My hosts are young, urbane, bohemian and widely travelled. We're speaking English, because their English is excellent and my Farsi doesn't extend beyond "hello" and "thank you".

I had met Dar on the train from Istanbul three weeks earlier. He's an assistant director in films, but is out of work. The other two are his cousins, a teacher who has spent a long time abroad, and an artist who lived in Europe for many years.

They are the most unusual Iranians you could imagine, as a foreigner. Indeed, this is one of the most unusual evenings I've had here, and one of the most stimulating.

I don't know how many social rules I was breaking. Perhaps none. But rules are definitely being broken. For a start, we're drinking vodka as we sit around the table eating olives and pistachios. Drinking alcohol is forbidden in Iran since the revolution in 1979 that brought the Islamic Republic into being. Having alcohol in your possession is certainly banned. Being Iran, the punishment for breaking either rule is likely to be severe.

The vodka is in an "Absolut" bottle. The bottle runs empty, and I'm slightly embarrassed that we've polished off what must be a prized possession. But one of the three produces a small, plastic jerry-can from a cupboard, and refills the bottle. We've been drinking Iranian hooch. And it seems that, whatever the official line might be, lots of other middle class Iranians are doing so too.

The conversation has been wide ranging. But when the discussion turns to religion, it occurs to me that I might have put my foot in it. From the evidence of the evening, I assume my hosts are not religious. But, when questioned about religious belief, not just cultural issues about Christianity and religion in the west, I find myself in trouble. Dar, the assistant director, is incredulous that people could not believe in God. He's not horrified, or annoyed, or offended. He simply cannot believe it. To not believe in a god is something he has never before considered, and apparently, cannot comprehend.

Iran is a paradoxical place. As an outsider it's difficult not to cross her borders without a head-full of baggage: images of the Islamic Revolution; of Ayatollah Khomeini; of the eight-year war between Iran and Iraq; TV pictures of Friday prayers at Tehran University, and hordes of black-clad men beating themselves about the head in grief and rage.

Iran, to the outsider fed on a diet of TV pictures, is a place of extremes, a dangerous place, the kind of place you think twice about visiting. But, I suspected that there might be more to Iran than meets the western eye through newspapers and television.

The Iranians were, almost without exception, warm, friendly people. They were curious to know what an outsider thought of their country. They were full of information, and went out of their way to make me feel welcome and at home. They wanted to impress on me their distinctness, their separate Persian identity, language, and long history. They wanted me to know that they are not Arabs.

In one revealing encounter I was asked what Farsi words I knew. I said I only know a few, "hello", "thank you", "good-bye". The people I was talking to quizzed me: what's the Persian word for "thank you"? "Motashakeram", I told them - the word that might be used on formal or official occasions. They weren't impressed. Yes, it's correct, but it's an Arabic word, I was told. The Persian word for "thank-you", the word the people use, is "merci". I'm not sure if the irony was lost on them.

Sadly, many Iranians also wanted to talk about their dissatisfaction and frustration with the system that rules them. Time and again people explain how they felt their lives were impinged upon by the police, the state, and the religious, which all appear to be synonymous. Many people said privately that they were not free, some thought that they were being impoverished while the ruling coterie enriched themselves on the country's resources, sometimes in the name of the Islam they claimed to protect.

For all their sense of self and pride in their country, many of the people I met wanted to leave. They wanted to emigrate to England, to Canada, or the United States. They pursue further education as a ticket out, a way to get visas and later jobs in the West. One man I met was prepared to pay a huge sum of money in valuable hard-currency to be smuggled into Europe.

I found a strange, slightly depressing mixture of frustration and pride.

Six hours south of the capital, Tehran, is the country's second city. Esfahan is the jewel in the crown. It is justifiably considered one of Persia's masterpieces, a royal city outfitted as much for pleasure as for administration and worship. To this day it remains apart, more relaxed, and somehow more sophisticated than sprawling, choking Tehran.

There is a public holiday in full swing, and the city is full of tourists, overwhelmingly Iranian. Not for the first time since arriving here, I feel secretly glad that Iran is not on the international tourist trail. If it was, Esfahan would be overrun with coach tours.

The city is famous for its bridges, palaces, and grand spaces. It has one of the region's great bazaars, and with well watered parks and shady trees, it must be one of the most pleasant cities for strolling and relaxing in the Middle East. It's famous for its carpet sellers, tea-houses, and a sweet called gaz. Above all it's famous for its buildings.

The central square, renamed the Emam Khomeini Square after 1979, but still known locally by its older name, is dominated by some of the masterpieces of Islamic religious architecture. The Emam Mosque and the smaller Sheik Lotfollah Mosque are awe inspiring works of form, symmetry, light and colour. They are breathtaking, extraordinary places of worship and adoration.

But, sitting quietly on the other side of the river, is one of Esfahan's enigmas. Highly regarded for their skills and enterprise, Shah Abbas I decided to relocate an entire community of Armenians around the start of the 17th century. They came with their families, their traditions and foods, and they brought their religion to what is now the suburb of Jolfa. And, in this great Islamic city in the centre of the Islamic Republic, there is still a Christian community, an important cathedral, and some small, but fabulously painted churches.

Sadly, the cathedral is shut when I arrived, and there's consternation outside. A wedding party has just left, there's a fierce debate going on at the gate as the custodian rudely refuses to let any pilgrims in, and then there is a car crash - a common occurrence on Iran's crazy roads.

I give up. It's clear that nobody is getting in. The pilgrims and I disappear down the narrow, deserted Friday streets. I know from a guidebook that there are churches in the area, but the map is inaccurate and the streets too complicated. Looking up, I follow the domes.

The Church of Bethlehem is famed for its frescos, some of which are said to be better than those in the cathedral. But the church feels like a museum. There is nobody there, there are no pews. It seems like a place that people come to, occasionally, to look at the paintings, but no longer to worship.

That said, the paintings are wonderful, scenes from the life of Christ and Old Testament stories beneath a dramatic black and gold dome. And there is a remarkable series of images depicting martyrs being brutally and graphically tortured to death. They are disturbing pictures, painted in a slightly flat, naive style, but an uncomfortable reminder that practicing their religion has not been a bed of roses for the Armenians. The cartoon-like violence of these death scenes seems to be informed as much by familiarity as by any desire to shock.

My guidebook says the Maryam Church is less impressive. But it strikes me more than the Bethlehem Church. There's a small child playing in the walled courtyard, a woman doing household chores, and a green, shady tree. Inside the church, the lights are on, and prayer books are on the pews. At the front of the church some kind of meeting is going on, but they finish and leave soon after I arrive. Like the Bethlehem Church, every foot of wall is covered in frescos. To western eyes they appear overwrought, even gaudy. But looking at them, their comic-book simplicity, all the Biblical narratives come to life vividly.

The priest, or perhaps the custodian, a big, bearded man, is happy to allow me wander about, and then turns off the lights and locks the door as I leave.

Outside the compound, the narrow street is deserted. Walking back towards the river, I'm greeted by an old man on the street. He shakes my hand and struggling to make himself understood in English, enquires where I'm from, and whether the Irish people are Christians. His family is Christian, he tells me, as he tries to express some hardship, or difficulty, or fear his family has experienced. He struggles to ask for information about Ireland. I think he's asking how his daughter might get there, but we stumble over the language barrier. I only vaguely understand what he wants to tell me, and he does not fully understand my requests for more information, for confirmation of what I think he's saying. We're both stuck, trying to communicate, but failing.

In the end he shrugs his shoulders and gives up, shakes my hand formally, and walks back into the courtyard of his house, shutting the gate. Understanding is something that needs careful cultivation between our different cultures.