Egypt has unveiled its plan to build a new administrative and business capital that will house five million people and feature a theme park "four times bigger than Disneyland".
Housing minister Mustafa Kamel Madbuli said the new 70,000 acre city, east of Cairo, would take five to seven years to build at a cost of $45bn (£30bn).
Details on how it would be funded were not revealed.
"The idea to build the new city originated from our awareness that Cairo's current population (18 million) will double in the next 40 years," Mr Madbuli said at a conference showcasing the details.
The proposed city would have "large green spaces, an international airport, a theme park four times bigger than Disneyland in California, 90 square kilometres of solar farms, and an electric train" to link with Cairo, Mr Madbuli said.
Parliament, presidential palaces, government ministries and foreign embassies would move to the new metropolis.
The plan for the new city was first announced in the summer of last year, but further details were kept under wraps until now.
President Abdel Fattah al Sisi is hoping the plan will help kick-start Egypt's troubled economy.
Mr al Sisi, who has positioned himself as a bulwark against Islamic extremists, said investing in the Arab world's most populous country would help stabilise the entire region.
Egypt's stability "is a cornerstone in regional stability," he told the conference in the Red Sea resort of Sharm el Sheikh.
Arab states including Kuwait, the United Arab Emirates and Saudi Arabia pledged $12bn in investment aid.
US Secretary of State John Kerry, who was at the gathering, said Washington stood beside Egypt as it seeks to recover from years of turmoil.
Mr Kerry, who earlier met Mr al Sisi and the leaders of Jordan and the Palestinian Authority, told businessmen that Washington was "eager and ready and willing" to help Egypt's economic development.
But a US diplomat travelling with him said there had been "no decision" on freeing up $650m in military aid frozen during the height of a crackdown on Mr al Sisi's Islamist opponents that left hundreds dead.
