Is Tehran coming to the end of its days as a capital city?
Iran's rulers are considering plans to relocate the country's capital. They say Tehran is in danger of being struck by a major earthquake. So how easy is it to move a capital out of a city, and where might Iran's go? Penny Spiller reports.
Tehran is a sprawling metropolis at the foot of the Alborz mountain range. It is home to some 12 million people, and is the largest city in the Middle East.
Not only is it the political and economic heart of the country, the city has a cosmopolitan air with its museums, art galleries, parks and universities. It has been Iran's capital since 1795.
But now a powerful state body, the expediency council, has approved plans by Supreme Leader Ayatollah Ali Khamenei to end Tehran's days as a capital.
These plans are not new. They are part of a long-term strategy to see the capital moved by 2025, and will need approval from many more government bodies before any relocation begins.
The government is said to be reacting to calls from Iranian seismologists, who have long warned that Tehran lies on at least 100 known fault lines, and would not survive a major quake intact.
The devastating earthquake that killed some 40,000 people in the south-eastern city of Bam in 2003 has certainly concentrated minds on the issue.
But the timing of this decision - coming as it does months after some of the worst anti-government riots Tehran has ever seen - is interesting, says Dominic Dudley, deputy editor of the London-based Middle East Economic Digest.
Tehran is very much a liberal enclave in Iran, he says - and it was many of those liberals who took to the streets complaining of fraud when conservative incumbent Mahmoud Ahmadinejad was declared winner of June's presidential election.
"It is tempting to view anything going on in Iran these days through the lens of that dispute," Mr Dudley told the BBC. "It certainly wouldn't hurt the government to move away from the big centre of liberal protests and opposition."
But where would it move to?
Iranian seismologist Professor Bahram Akasheh told the Guardian newspaper that a new capital should be built between the holy city of Qom and Delijan, in Markazi province.
This is an area, he said, that has not seen an earthquake in 2,000 years.
However, Qom is the spiritual home of Iran's conservative Islamic establishment. Moving the capital nearer to Qom could be seen as a sign of the conservatives stamping their authority, says Mr Dudley.
Wherever the capital moves to, and for whatever reasons, the government will have some other important considerations to take into account if creating a capital from scratch, says Andrew Jones of the engineering, planning and architectural design firm AECOM.
It is all very well moving government buildings and staff, but the new city will flounder if it has no cultural life and its economy is solely driven by the government.
"Generally, our capital cities are economic powerhouses as well as seats of government. That takes a long time to bed in," he told the BBC.
"A new city generally takes 10 to 20 years to build, it takes a century or more to mature into something that is an attractive and self-sustaining place."
Brazil's capital, Brasilia, might be an interesting example for the Iranian authorities to study.
It was built because the coastal location of the old seat of power, Rio de Janeiro, was deemed too far from large swathes of the country.
So the new capital was unveiled in a remote part of central Brazil in 1961.
Claudio de Magalhaes, senior lecturer in planning and urban regeneration at University College London, said this location suited the military government that came to power three years later.
Brazil: Brasilia, 1961
Tanzania: Dodoma, 1973
Ivory Coast: Yamoussoukro, 1983
Nigeria: Abuja, 1991
Kazakhstan: Astana, 1997
Burma: Naypyidaw, 2005
"One of the things about a new capital is that it tends to insulate the government from the pressures and influences of the big city," he said.
"The military government found it very convenient to have the political class away from the city. You don't have any demonstrations on your doorstep. It's very easy to close the airport and access to the city whenever you see fit, which happened in the early days of the government."
In the beginning, Brasilia was inhabited mostly by people whose livelihoods depended on the government.
But over the years it grew, and grew, and grew - confounding the planners' expectations.
"What no-one had predicted was the growth in the satellite areas around the city. These were places peopled by construction workers, cleaners for government buildings, mechanics for employees' cars," Mr Magalhaes told the BBC.
In the early days, land in the centre of Brasilia - known as the pilot plan and now a Unesco heritage site - was compulsorily purchased and given to government ministries who were then able to offer homes to staff.
But as these assets were sold off, they reaped huge profits for the buyers as increasing numbers of people moving to the city sought to live in that area, Mr Magalhaes said.
"It distorted the market. And you had this strange situation whereby large houses with swimming pools outside Brasilia were much cheaper than a small flat in the centre," he said.
The total cost of moving Brazil's capital from Rio to Brasilia is so huge it has never really all been accounted for, Mr Magalhaes believes.
Even 20 years after Brasilia was created, the government was still having to pay premiums to get people to move there, he adds.
Losing its capital status also had a huge effect on Rio, which had already seen its economy suffer as businesses migrated to Sao Paulo.
"Local politics became very low level and was dominated by its relationship with the drug lords," Mr Magalhaes said.
Andrew Jones of AECOM believes Tehran will also have a tough period of adjustment if it goes the same way as Rio.
"Although the underlying character of the city will stay, it will lose the added extras that come with being home to the seat of government. It will start to lose cultural institutions and some other components that make it a powerful place," he said.
"But I think Tehran will survive. It has been a major city for thousands of years, so it will recover and remake itself."