The last in a series of reports from northern Nigeria by the BBC's West Africa correspondent, Mark Doyle, assessing the impact of the 11 September attacks

This is a very unusual city. It is both a symbol of national unity and a rather un-Nigerian sort of place.

Officials say Abuja exudes harmony

Conceived in the 1970s, begun in the 1980s, and still under construction today, Abuja has none of the groaning population problems of Lagos, none of the dusty, Sahelian atmosphere of Sokoto or Maiduguri.

It has not experienced the violence prevalent in other parts of Nigeria. The Christian-Muslim tensions of Kano and Kaduna, for example, are relatively hidden here, and that is exactly the way Abuja was planned to be.

Right in the geographic heart of Nigeria, Abuja was conceived as a capital where all of the country's ethnic groups, tribes and religions would come together in harmony.

Abuja was the place to seek the government's point of view on whether the war in Afghanistan had influenced life decisively in Nigeria.

An extraordinary city

I had already seen echoes of the "War Against Terrorism" (or 'Jihad Against America', depending on your point of view) in Kano and Kaduna. The burnt out churches and mosques and the photos of Osama Bin Laden in taxi cab windows were still fresh in my mind.

What we have built here is a real symbol of togetherness, where we can feel at home

Abuja official

But no visit to the federal capital of Nigeria would be complete without first describing this extraordinary city.

Every time I come here I stand on the top floor of one of the new buildings, look out over the city, and imagine I have set out before me is a sort of giant children's construction toy.

The new buildings set in their virgin sites look like set-piece models which I imagine to myself I could just pick up and re-arrange.

There is no shortage of magnificent edifices in Abuja, from the National Mosque with its golden dome glistening in the sun, to the bright pink Federal Secretariat Complex, to the still-being-built National Sports Stadium.

Much of the city is still under construction

However, in Abuja it is as if none of these places is connected. The ubiquitous Julius Berger PLC may have constructed fine roads between all the sites, but the toyset is still not really a joined-up place.

There is no real organic centre to this city, but my candidate for town centre is the lobby of the Hilton Hotel, a 600-roomed mountain of a hostelry.

The Nigerian way

It's the closest thing Abuja has to a village square, but one reserved for the rich and powerful only, the "Big Men" (and Women) of Nigeria's elite.

But that is the Nigerian way.

The mosque is one of the city's many magnificent edifices

On any day in the copper-coloured, soft-lit lobby of the Hilton you'll see politicians in their magnificent traditional robes sweeping through, pursued by a train of sidekicks and sycophants.

You'll see Nigerian businessmen in Saville Row suits, Texas oilmen with Stetson Hats, and dusty German construction foremen in shorts and T-shirts. The lobby of the Hilton is a microcosm of what makes Abuja tick.

Cynics say Abuja was first perceived by Nigerian politicians as a great place to milk the oil boom money - by distributing billions of dollars worth of building contracts and kickbacks.

"That's an unfair view," said an official from the ministry responsible for running Abuja, "what we have built here is a real symbol of togetherness, where we can feel at home, whether we're from the north, south, east or west".

The proof of this, the official said, was that even when foreigners came here they felt harmony.

New buildings in Abuja look like set-piece models

"We hosted talks between Britain and Zimbabwe," he said, "and they solved their problems together almost immediately".

This was an extravagant claim, Nigerian-style, but it did capture the essence of the official vision of Abuja.

I asked Nigeria's Minister of Information, Professor Jerry Gana, if he thought the war had spilled over into Nigeria.

"Not really", he replied "not in a direct sense," he said.

The minister was rummaging through his diplomatic tool bag up as he spoke.

Treading with care

The federal government, very understandably, has to tread a fine line on religion. The great power blocks of Nigerian politics are broadly centred on the North and the South, Muslim and Christian.

Problems tend to arise when one particular social or tribal group fears domination by an incoming group

Information Minister Jerry Gana

A subject like Afghanistan has to be treated with care.

The federal government line appears to be basically pro-American but tempered with appeals for restraint when it comes to civilian casualties.

No-one will say this in as many words; when the foreign minister came close to it, many people think it was his stand which angered Muslims and led to the Kano religious riots of October in which more than 100 people were killed.

Mr Gana's thesis was, broadly, that if there are communal tensions in Nigeria it is more to do with economic hardship and social exclusion than ethnicity or religion.

"Problems tend to arise," the minister said, "when one particular social or tribal group fears domination by an incoming group. Now, if that fear is fuelled by one group being Muslim and one being Christian, then there is confrontation. But deep down the initial cause is not religious. It is largely political, economic and social."

Information Minister Gana: Blames tensions on economic hardship

It is perhaps reassuring to think that communal violence has real social causes, and therefore, potentially at least, real solutions.

Otherwise, we would have to conclude that Nigerian Muslims and Christians (or any of a number of opposing ethnic groups) kill each other simply because they harbour burning fundamental hatreds.

That's a conclusion I wouldn't want to draw. And its one which the Nigerian Government, sitting astride a cauldron of ethnic and religious disputes, dare not draw.