ONE OF Osama bin Laden's many half-brothers, Tarek bin Laden, this week signed a deal with tiny Djibouti which may—or may not—mark the start of one of the world's boldest engineering projects. Djibouti's president, Ismael Omar Guelleh, promised Mr bin Laden 500 sq km (193 sq miles) of land to start building Noor City, the first of a hundred “Cities of Light” the vast Saudi Binladen Group plans around the world. “A hope for all humanity, the first environmental city of the 21st century,” gushed the promotional video at the signing. The audience, mostly American military contractors near retirement age, clapped enthusiastically. Engineers elsewhere say the scheme is a fantasy.

Mr bin Laden, his sons, and their front man, Muhammad Ahmed al-Ahmed, a Saudi former shipping executive, say they have already invested “hundreds of millions of dollars” in a plan to build cities on either side of the Bab al-Mandib (Gate of Tears) strait at the foot of the Red Sea. Construction is supposed to begin next year, after the terms of sovereignty for the tax-free metropolises have been agreed. By 2025, says Mr Ahmed, Djibouti's Noor City will have 2.5m people and its Yemeni twin 4.5m. Several million jobs will be created. An airport serving both cities will, he says, attract 100m passengers a year. A 29km bridge across the strait will connect Arabia and Africa by road, rail and pipelines, its towers among the tallest on earth. The cost? A mere $200 billion or so.

Yet oddly, aside from Djibouti's, no African government officials were to be seen, no architect, no technical adviser to explain how the cities could run on renewable energy, and barely an engineer. None of the Noor City delegation noted that blazing hot Djibouti, with 800,000 people, is already acutely short of water and imports nearly all its food, that 150,000 of its people are “facing imminent starvation”, according to the UN's World Food Programme, and that millions more are famished in next-door Ethiopia. Mr Ahmed also brushed aside any worry about instability in Yemen, where an al-Qaeda suicide bombing on July 26th targeted the country's police. Yet at the last moment Yemen's government refused visas to journalists travelling with Mr bin Laden.

Mr Ahmed has worked for DynCorp, an American military contractor. So had one of the project's main managers, Michel Vachon, before moving to L3 Communications, a contractor often employed by the American government. Another manager, Dean Kershaw, spent 29 years in America's forces; some others had served in the Bush administration. Armed American special-forces veterans now apparently employed as security guards by L3 chaperoned journalists. All part of an American plan to help secure the Suez shipping lane or to strengthen the hand of friendly forces in Yemen? “Absolutely not,” said Mr Kershaw. “The [American] government has vetted us, but they're not behind us.”

Whatever the reality, the presence of arms manufacturers in the consortium, including Allied Defense Systems and Lockheed Martin, will fuel conspiracy theories among Arabs. Mr Ahmed says investors in Djibouti's Noor City have the chance to “be part of modern humanity” by creating the “financial, educational, and medical hub of Africa”. Africans may wonder why the hub is not being built in a bit of Africa where more Africans live and which has food and water.

Unlike the Gulf States, which financed most of their development from oil revenue, Djibouti and Yemen are too poor to provide more than scrubland. Mr Ahmed says his firm will finance a new railway through Yemen to connect the new cities with Dubai. He is vaguer about Africa, where a motorway and railway would have to be built to Addis Ababa, Ethiopia's capital, and on to Kenya's Nairobi and Sudan's Khartoum, if it is really to help perk up the continent's economy.