Egypt has unveiled an official plan to construct a massive new capital city in a deal which could cost $45 billion.

The new capital city, which will be located next to Cairo, will be constructed with funding from Gulf states and will house five million people.

“We are talking about a world capital … 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,” Housing Minister Mustafa Kamel Madbouli said during a press event.

The project will be led by self-made UAE billionaire Mohammed Alabbar, whose company Capital City Partners group has constructed the Burj Khalifa — the tallest building in the world, located in Dubai — and is constructing an even more expensive megapolis: the King Abdullah Economic City, in Saudi Arabia.

Capital City Partners group has promised that the new city will be “sustainable,” with 90 square kilometers of solar panels and an electric railway that will connect it with the current Egyptian capital.

Investment Minister Ashraf Salman has estimated that the development of the new city would take about twelve years, however Housing Minister Mustafa Kamel Madbouli said the city would be completed in around five to seven years, which would require a breakneck pace of construction.

The plans for the new city follows a pledge of $12 billion of investment to Egypt from Gulf Arab allies on Friday, which was a big boost to President Abdel-Fattah al-Sisi as he continues to work on reforming the economy following years of political upheaval and grapples with recent attacks by militant groups opposed to his government.

The new pledge of investment adds to the total of over $20 billion that has already been contributed to the nation since the military ouster of President Mohamed Morsi nearly 20 months ago.

Kuwait, Saudi Arabia, and the UAE (United Arab Emirates) each offered $4 billion in investment to Egypt on Friday.

“The aim is to put Egypt back on the map of international investment, and send a message to the world that the country is safe and attractive,” said International Cooperation Minister Naglaa al-Ahwani during a press event on the plan to construct the new capital city.

Egypt has suffered a collapse of its tourism industry, which is a major source of hard currency, following the the Arab Spring of 2011.

The pledge of investment will help boost Egypt’s balance sheet as its international reserves fell to around $15 billion in January, down from $17.3 billion a year earlier and $36 billion before the uprising in 2011.