The host of the 2030 World Expo will be chosen on Tuesday, with Rome in Italy, the Saudi capital Riyadh and South Korea's Busan contending to welcome the showpiece event held every five years.
The World Expo -- which traces its history back to the 1851 Great Exhibition in London and the 1889 Exposition Universelle in Paris that saw the construction of the Eiffel Tower -- is a months-long mega event attracting millions of visitors that aims to respond to the specific challenges of the current time.
The hosting of the Expo is regulated by the Paris-based Bureau International des Expositions (BIE), whose 182 member states will vote for the winner at a conference in the French capital during the afternoon.
This year's event has been the subject of particularly intense lobbying from Italy, Saudi Arabia and South Korea, whose governments are all keen to have the honour of the 2030 World Expo.
Saudi Crown Prince Mohammad bin Salman has been at the forefront of his country's efforts to host the Expo, which would be the latest in a line of events to be held in the kingdom despite concerns over its rights record.
The kingdom is set to host the 2034 football World Cup after emerging as the only bidder for the event.
But Rome and Seoul have not stinted in their efforts either.
South Korean President Yoon Suk Yeol was in the French capital only last week to make a final pitch for Busan's bid, while Italy's far-right Premier Georgia Meloni has pressed Rome's cause in Paris and elsewhere.
- 'History of rights violations' -
Awarding the Expo to Saudi Arabia could prove controversial.
Activists argue the kingdom cannot be rewarded for violations of human rights, including the 2018 murder of dissident journalist Jamal Khashoggi in the Saudi consulate in Istanbul.
Groups including MENA Rights Group, Freedom House and Paris-based NGO Together Against the Death Penalty (ECPM) last week wrote an open letter urging against choosing Riyadh "given its appalling human rights situation".
"By providing a global platform to a regime with a history of violating basic human rights and curbing freedoms, the international community risks sending a tacit message that such actions are acceptable," it said.
Saudi, one of the world's top executioners, put to death 112 people between January and October this year, according to Amnesty, while rights groups accuse it of stifling dissent.
French President Emmanuel Macron had already given Riyadh Paris's backing when he held talks with the crown prince at the Elysee in July 2022, a move that caused some irritation in Italy, France's neighbour and European Union partner.
- Russia, Ukraine out -
The host is chosen at the BIE's general assembly on Tuesday after the candidates each make a final presentation of their bid.
If no candidate wins a two-thirds majority in the first round, the secret voting then goes to a run-off between the two top bids, with just a simple majority then needed.
Every member state -- large or small -- has a single vote, meaning a vast global campaign is needed to ensure victory.
Busan wants to hold the Expo from May to October 2030 on the theme "Transforming Our World, Navigating Toward a Better Future".
Rome plans the Expo in the same period to be about "People and Territories: Regeneration, Inclusion and Innovation".
A Riyadh Expo would be from October 2030 to March 2031 on the theme "The Era of Change: Together for a Foresighted Tomorrow".
The most recent World Expo took place in 2020 in Dubai and the next World Expo is due in 2025 in Osaka, Japan, on the theme "Designing Future Society for Our Lives".
Other bids for 2030 came from the Russian capital, Moscow, and the Ukrainian city of Odesa.
Russia withdrew its bid in May 2022, shortly after its invasion of Ukraine, while Odesa did not make the final shortlist of three announced in June.