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Oxus chariot model (made almost 2,500 years ago). Gold - from the Ancient Persian Empire

This week we're in very exalted intellectual company: we're with Confucius in China, Pericles in Greece, and Cyrus in Ancient Persia. It's the fifth century BC, and across the world societies are beginning to articulate very clear ideas about themselves and about others. They're inventing and defining what we would now call statecraft. This is the era of what some have called the 'empires of the mind'. I'm going to begin with the world superpower of two and a half thousand years ago: Persia.

"This was an empire that was run on a rather different principle to previous empires - which were really based on might being right." (Michael Axworthy)

"Persian occupation - I suppose you could compare to a light morning mist settling over the contours of their empire - you were aware of it, but it was never obtrusive." (Tom Holland)

We are about 70 miles north of Shiraz, Iran, and the low camel-coloured hills have opened out into a flat windy plain. It's pretty featureless landscape, except that right in front of me is a huge stone plinth, rising in six gigantic steps to what looks like a gabled hermit's cell. It dominates the entire landscape. It is the tomb of Cyrus, the first Persian emperor, the man who two and a half thousand years ago built the largest empire that the world had then seen, and changed the world - or at least the Middle East - for ever.

Centred in modern Iran, the vast Persian Empire ran from Turkey and Egypt in the west to Afghanistan and Pakistan in the east. To control an empire like this required land transport on a quite unprecedented scale, and so the Persian Empire is the first great 'road' empire of history.

In front of me now [in the British Museum] is a chariot made of solid gold and pulled by four golden horses. It's easy to imagine a chariot like this racing along those great Persian imperial roads. It's got two figures in it: the driver, who stands holding the reins, and the much larger and clearly very important passenger, who sits on a bench at his side. He is probably meant to be a high-up administrator, visiting the distant province that he rules on behalf of the King of Persia.

And this chariot was found in a very distant province, right on the far eastern edge of the empire, somewhere on the borders of modern Tajikistan and Afghanistan. It's part of a huge hoard of gold and silver objects, which for over a hundred years have formed one of the great collections here at the British Museum.

This magnificent chariot sits quite comfortably on the palm of my hand, where it looks like an exquisite toy for a privileged child. We can't be certain the chariot was in fact a toy; it could have been made as an offering to the gods, either asking them for a favour or thanking them for one. But whatever it meant then, this tiny golden chariot allows us today to conjure up a whole empire.

But what kind of an empire was it? It was more a collection of kingdoms than what we might immediately think of as an empire. Cyrus called himself the Shahanshah - the King of Kings - making clear that this was a confederation of allied states, each with their own ruler but all under firm Persian control. It was a model that allowed a great deal of local autonomy and all sorts of diversity - very different from the later Roman model. Here's historian and writer Tom Holland:

"The Roman approach, of course, was to encourage those they had conquered to identify with their conquerors, so that ultimately everyone within the borders of the Roman Empire came to consider themselves to be Romans. Persians went for a very different approach, in that the method that the Persian kings liked to employ with those they conquered was to encourage the elites, in particular, to collaborate. So as long as you paid your taxes, and you didn't revolt, then you'd pretty much be left alone. That said, however, you do not conquer a vast empire without spilling an immense amount of blood, and there was no question that if you dared to stand up to the Persian kings then you would be obliterated."

And they obliterated troublesome people by sending their armies along those wonderfully straight and fast imperial roads. But bloodshed was generally avoided, thanks to a huge - and hugely effective - administrative machine. The King of Kings, of course, controlled everything, but at local level he was represented by a governor - a satrap - who would keep a close eye on what was going on in these subordinate kingdoms. He would enforce law and order, levy taxes and raise armies.

Which brings us back to our golden toy - because the passenger in our chariot must be a satrap on tour. He sports a stylishly patterned overcoat - he's obviously spent a great deal of money on it - and his headdress leaves you in no doubt that this is a man who is used to being in charge. His chariot is made for serious travel: the large-spoked wheels are as high as the horses themselves, and are clearly designed for long distances.

Nothing tells you more about a state than its transport system (you need think no further than modern Britain), and so our chariot tells us a great deal about imperial Persia. Public order was so secure that people could travel long distances without armed guards. And they could travel fast. With its horses specially bred for strength and speed, and with its large, steadying wheels, this chariot was the Ferrari or the Porsche of its time. Broad dirt roads were kept wheel-worthy in all weathers, and there were frequent staging posts. Commands from the centre could be transmitted at speed across the whole territory, thanks to an entirely reliable royal postal service that employed horsemen, runners and express messengers. Foreign visitors were deeply impressed, among them the Greek historian Herodotus:

"There is nothing in the world which travels faster than these Persian couriers ... it is said that men and horses are stationed along the road, equal in number to the number of days the journey takes - a man and a horse for each day. Nothing stops these couriers from covering their allotted stage in the quickest possible time - neither snow, rain, heat, nor darkness." (Herodotus, History VIII. 98)

But our chariot doesn't just tell us about travel and communications; it sums up the diversity that was at the heart of the Persian imperial system. Although found on the eastern frontier near Afghanistan, the technique of its metal-working shows that it must have been made in central Persia. The driver and his passenger wear the costume of the Medes, and on the front of the chariot, prominently displayed, is the head of the Egyptian god Bes. Now Bes, a dwarf figure with bow legs, is perhaps not your most likely candidate for a divine protector, but he looked after children and people in trouble, and he was a good god to have guarding your chariot on long journeys. I suppose he's the equivalent of a modern-day saint or talisman dangling from the car mirror.

But what, you might ask, is an Egyptian god doing protecting a Persian on the frontiers of Afghanistan? Well, it's a perfect demonstration of the Persian Empire's striking capacity to tolerate different religions and indeed, on occasion, to adopt them from the people that they conquered. This unusually inclusive empire was also perfectly happy to use foreign languages for their official proclamations. Here's Herodotus again:

"No race is so ready to adopt foreign ways as the Persian; for instance, they wear the Median costume as they think it handsomer than their own, and their soldiers wear the Egyptian corselet." (Herodotus, History I. 135)

The multi-faith, multi-cultural approach that's summed up in our little chariot, when combined with huge military power, created a flexible imperial system that lasted for over two hundred years. It gave the king the opportunity to present the image of a friendly empire - whatever the facts on the ground might actually have been. So, when Cyrus invaded Babylon, near modern Baghdad, in 539 BC, he could issue a grandiloquently generous decree - in Babylonian - presenting himself as the defender of the people that he had just conquered. In his own words:

"When my soldiers in great numbers peacefully entered Babylon ... I did not allow anyone to terrorize the people ... I kept in view the needs of the people and all their sanctuaries to promote their well-being ... I freed all slaves."

The most famous beneficiaries of Cyrus' shrewd political decision after the conquest of Babylon were the Jews. Taken prisoner a generation before by Nebuchadnezzar, they were now allowed to return home to Jerusalem and to re-build the temple. It was an act of generosity that they never forgot. In the Hebrew scriptures, and especially by the prophet Isaiah, Cyrus is hailed as a divinely inspired benefactor and hero. And in 1917, when the British government declared that it would establish in Palestine a national home to which Jews could once again return, images of Cyrus were displayed with photographs of George V throughout eastern Europe. Not many political ploys are still paying dividends like that, two and a half thousand years later.

One of the perplexing things about the Persian Empire is that the Persians themselves wrote very little about how they managed it. Most of our information comes from Greek sources and, as the Greeks were for long the enemies of the Persians, it's rather as though we knew the history of the British Empire only through documents written by the French. But modern archaeology has provided new sources of information, and in the last 50 years the Iranians themselves have rediscovered and re-appropriated their great imperial past. Any visitor to Iran today feels it at once. Here's Michael Axworthy, Director of the Centre for Persian and Iranian studies at the University of Exeter, and the author of 'Empire of the Mind' - a history of the enduring ideal of the ancient Persian Empire:

"There is a huge and unavoidable pride in the past in Iran ... It's a culture that is at ease with complexity, that has faced the complexity of different races, different religions, different languages, and has found ways to encompass them and to relate them to each other and to organise them. Not in a loose way or in a relativistic way, necessarily, but in a principled way that keeps things together. And Iranians are very keen for people to understand that they have this long, long, long history and this ancient heritage."

Axworthy's phrase 'empires of the mind' sums up pretty well the theme that I'm trying to tackle this week, but perhaps 'states of mind' would be more accurate - because I'm talking about objects that show us how different people imagine and devise an effective state. For Persia I've been looking at a toy chariot; for Athens I'll be looking at a temple. As you'd imagine, because they for so long were at war, Greeks and Persians had very different ideas of what a state should be. But precisely because they were at war, each tended to define the ideal state in opposition to the other. In 480 BC Persian troops destroyed the temple on the Athenian Acropolis. In its place the Athenians built the Parthenon that we know today.

There are few objects that over the last two hundred years have been so widely seen as embodying a set of ideas as the Parthenon. And I'll be looking at one of the sculptures that decorated it in the next programme.