More about Kazakhstan and its stunning new constructions: The Pyramid

Lord Foster, 69, has designed some audacious buildings in his time, from the much-loved "Gherkin" tower in London to Beijing's new airport - right now the world's biggest construction site. He has designed - but never built - the world's tallest towers. But nothing he has done to date compares with this latest job. Because nobody asks for buildings like this. Unless you happen to be President Nursultan Nazarbayev of Kazakhstan.

With a massive oil, gas and mineral industry behind him, investors falling over themselves to catch his eye, and not much by way of political opposition, Nazarbayev can build whatever he wants in his showpiece new capital of Astana, being built according to a monumentally axial 1998 Kisho Kurokawa masterplan. And what Nazarbayev wants is religious and ethnic reconciliation.

He also wants an opera house to rival Glyndebourne or Covent Garden, a national museum of culture, a new "university of civilisation", and a centre for Kazakhstan's ethnic and geographical groups. All these will be slotted into Foster's pyramid, which is 203 feet tall and 203 feet square at the base (62m by 62m). The podium will contain an opera house.

So this is not just a talking-shop for clerics. Although with a population split 50:50 between Russian Orthodox and Muslim, and with extremism on the rise all round, you can see why it's on the president's mind. He hosted the first such congress of religious leaders in September 2003, and wants to make it a triennial event.

Made of a diamond-pattern latticework of tubular steel clad in pale silver-grey stone, the pyramid will climax in a great coloured apex of abstract modern stained glass. Bathed in the golden and pale blue glow of the glass (colours taken from the Kazakhstan flag), 200 delegates from the world's main religions will meet every three years in a circular chamber - based on the United Nations Security Council in New York. The chamber is perched high beneath the point of the pyramid on four huge struts intended, says Foster, to "symbolise the hands of peace". A research centre into the world's religions, complete with a large library, occupies the floor below.
For the general public, things are no less spectacular. The pyramid is raised on a low artificial hill - making it even taller - inside which is the 1500-seat opera house. Lifts rising up the inwardly-leaning walls - rather like the legs of the Eiffel Tower - carry you up to a middle level.

At this point more drama begins as you enter what Foster's colleagues calls "the hanging gardens of Astana". The atrium walls suddenly flare outwards, vegetation cascades round on all sides from planters set into the walls. To get up to the unearthly light pouring down from the top of the pyramid, you must walk up zig-zag ramps through these airborne gardens as if ascending to heaven.

Even Foster - not a demonstrative man - can hardly believe he has this job. "A few months ago, this didn't exist," he says as we stand in his Battersea studio in front of a six-foot tall working model of the pyramid. "It's the fastest thing that we've ever done. They've ordered the steel and it starts to be built next month. The scale of what is happening in Astana is incredible." The president works surrounded by models of the new Astana, his personal Brasilia or Canberra. He is pouring billions of dollars into it - despite the reported reluctance of his ministers, and international airlines, to make the move there from the old capital of Almaty near the Chinese border.

The climate is a problem. Temperatures in Astana range from minus 40 Celsius in winter to plus 40 Celsius in the heat of summer. It's not just a matter of insulating the building - it's coping with the yearly expansion and contraction of the huge steel and stone structure. It is being made in prefabricated sections during the winter, to be assembled in summer. Self-supporting as it rises, it will need no temporary props. The project cost is around 30 million dollars.

The project is being managed by a Turkish construction company, Sembol Construction.
Foster chose the pyramid shape because it is has no negative religious connotations. He has designed several concert halls, art galleries and museums, but says this has a greater importance. "It is primarily a cultural centre - but because it will host a peace congress of 18 religions, it becomes something else. It is about religion, peace and co-existence," he says. "It is dedicated to the renunciation of violence and the promotion of faith and human equality."