Sydney - Sydney will kick-start the global New Year's Eve party with its biggest fireworks display ever, but fear of jihadist attacks has cast a pall with Brussels scrapping celebrations and many cities tightening security.
The show from the Harbour Bridge and Opera House in Australia's largest city is traditionally the world's first major event to ring in the New Year.
Despite safety concerns, organisers are expecting a one million plus crowd before the chimes of midnight move across Asia, the Middle East, Africa, Europe and finally the Americas.
"It just keeps getting better every year," said Sydney Lord Mayor Clover Moore, "with 2,400 more fireworks on the bridge than ever before and a host of exciting new effects lined up".
The 2016 theme is "City of Colour" and seven tonnes of fireworks will go up in smoke, including 11,000 shells, 25,000 shooting comets and 100,000 individual "pyrotechnics effects".
Hong Kong, Beijing, Singapore and other Asian cities may rival Sydney's pyrotechnic splash, but Brunei offers a sober evening after banning Christmas in a shift to hardline Islamic law.
Jakarta remains on high alert after anti-terror police foiled detailed plans for an alleged New Year suicide attack in the Indonesian capital.
At the heart of Europe, annual festivities and fireworks in Brussels have been cancelled as the Belgian capital - home to NATO and the European Union - remains on high alert.
"It's better not to take any risks," mayor Yvan Mayeur said Wednesday after police arrested two people suspected of plotting to launch attacks during the festivities at Brussels landmarks.
The French capital, still reeling from the November 13 slaughter of 130 people, has also cancelled its fireworks display.
But authorities agreed France's biggest public gathering since the attacks can go ahead on the Champs Elysees avenue, with bolstered security.
"The people of Paris and France need this symbolic passage into the New Year," said Paris mayor Anne Hidalgo.
"After what our city has lived through, we have to send a signal to the world," she told the weekly Journal du Dimanche.
In Turkey, police have detained two Islamic State suspects allegedly planning to stage attacks in the centre of Ankara which is expected to be packed on New Year's Eve.
Meanwhile, in Moscow police will for the first time close off Red Square where tens of thousands of revellers traditionally gather.
"It's no secret that Moscow is one of the choice targets for terrorists," Moscow mayor Sergei Sobyanin said recently.
In Madrid, thousands of people will flock to Puerta del Sol square, however police will limit the number allowed in to just 25,000.
London is also trying to control the crowds by again charging for access to central riverside areas to see the fireworks, with more than 113,000 10-pound (US$15 (S$21)) tickets already sold.
Berliners will do better with about a million expected at the Brandenburg Gate for a free mega-street party.
Cairo meanwhile is trying desperately to attract tourists to bolster the economy.
The government is staging celebrations in front of the pyramids near the Egyptian capital, with ambassadors, artists and intellectuals all invited.
Egypt has been in turmoil since the 2011 uprising but was further hit by the October 31 crash of a Russian airliner over the Sinai killing 224 people.
On the nearby Gaza Strip, the Islamist group Hamas has banned public New Year's Eve parties.
Police spokesman Ayman al-Batinji told AFP such celebrations were "incompatible with our customs, traditions, values and the teachings of our religion".
In stark contrast, Sierra Leone's capital Freetown is hoping to reclaim its mantle as host of the best beach parties in Africa after Ebola scared people away.
The city of 1.2 million was deserted 12 months ago during the worst Ebola outbreak ever recorded.
"This New Year's Eve I am going to dance and party until the cock crows," said 35-year-old Franklyn Smith.
Celebrations away from the palm-fringed beaches will be muted, however, as people remember almost 4,000 victims of the epidemic.
In New York, despite a pledge of tight security for Times Square, another million people are expected to turn out to see the ball descend.
This year's show includes performances by artists Demi Lovato, Daya and Jessie J.