Five nations will compete to host Expo 2030.
On Friday, Saudi Arabia set out its bid for Riyadh to host the world's fair – just before the governing body, the Bureau International des Expositions, closed the window for applications.
Riyadh is up against the Russian capital Moscow, the Italian capital Rome, Ukraine's resort city of Odessa and South Korea's second city Busan.
The final decision rests on a vote by 170 members of the BIE in 2023.
Dimitri Kerkentzes, BIE secretary general, said the bids were evidence of the compelling interest in Expos.
“The BIE welcomes these five candidatures, which attest to the strong and shared desire for nations around the world to come together to shape a common vision for peace and human progress,” he said.
“The expression of these different visions for the future will be of interest to us all as we learn more about these candidatures in the project evaluation phase.”
All five bids will be examined, with each nation required to submit detailed dossiers of their proposals. The BIE will then organise inquiry missions to the countries to assess the feasibility each project.
BIE members will choose the host country in 2023 during a general assembly, with each nation allowed one vote.
All projects will be presented to members for the first time in December, and then in subsequent assemblies until the final vote.
Saudi Arabia proposes hosting the six-month Expo in Riyadh in October 2030 under the theme "The era of change: Leading the planet to a foresighted tomorrow".
Saudi Crown Prince Mohammed bin Salman has said the decision was taken to address “an unprecedented need for humanity’s collective action".
The UAE has declared it backs the kingdom's bid. Sheikh Mohammed bin Rashid, Vice President and Ruler of Dubai, said the experience gained in preparing for the Expo 2020 Dubai would be “available to our brothers".
Of the other bids, Italy is a founding member of the BIE and has hosted two expos – in Milan in 1906 and 2015 – as well as five specialised expos.
Specialised expos are held for three months on a specific theme. The 2017 Astana Expo on future energy was held in Kazakhstan.
The theme for Rome's expo bid is "The horizontal city: Urban regeneration and civil society".
Russia and South Korea have already presented their projects to the BIE general assembly at a video conference in June.
Moscow’s theme is "Human progress: A shared vision for a world of harmony", with the government saying that hosting the world's fair is a "national priority".
Busan’s theme is "Transforming our world, navigating towards a better future", which covers uniting people, technology and nature.
South Korea has experience of hosting two specialised expos.
Ukraine’s theme for its Odessa proposal is "Renaissance, technology, future".
Expos have been held since the Great Exhibition in London in 1851.
The global gathering of nations aims to find solutions to challenges facing the world and allows countries to build pavilions that millions of people can visit over six months.
Expo 2020 Dubai has recorded strong numbers, with more than 1.5 million visits since the opening day on October 1.
After the Expo ends in March next year, the focus shifts to Japan’s second largest city, Osaka, which will host the world’s fair in 2025 under the theme "Designing the future society for our lives".