London: With one year to go until the opening ceremony of the 2012 Games, London organizers completed the last of the Olympic Park's permanent venues on Wednesday and promised to put on a safe and spectacular event that will captivate the world.

Ahead of an evening ceremony in Trafalgar Square, the 269-million pound ($442-million) aquatics center was opened on the former industrial wasteland that has been transformed by one of Britain's biggest-ever building projects.

"I have seen so many venues in my life that I had a visual shock when I came in," said International Olympic Committee president Jacques Rogge, overlooking the swimming pool. "I came in from the top - everything stands out; the harmony, the quality, the innovation. It's a masterpiece."

Rogge was in London to formally invite the world's athletes to the games with few of the distractions that overshadowed the one-year countdowns to the previous two Summer Games.

Beijing was battered for its record on Tibet and human rights before the 2008 Olympics, while Athens struggled to the last minute to finish venues in 2004.

Even the worst global recession for more than 70 years failed to significantly derail London's plans, with test events already underway and the IOC relaxed about the final 12 months before the games returns to London after 64 years.

Security and transportation remain the biggest challenges.

The British government has been planning for the national terror threat to be classified as "severe" during the Olympics, meaning an attempted attack is highly likely. A day after London was awarded the games in 2005, homegrown suicide bombers attacked London's transportation network, killing 52 people.

"Security is permanently under review," organizing committee chairman Sebastian Coe said. "We have the right teams in the right place. We will do whatever we have to do to provide a safe and secure games."

"The key is finding the right balance," he added. "We do big events pretty well in this country. We want people to feel welcome without the city being locked down."

The latest milestone will be marked Wednesday evening by 17-year-old Tom Daley taking the first dive in the Olympic pool, days after qualifying for his second games.

The 17,500-capacity venue, which will also be used for swimming, synchronized swimming and water polo events, had been expected to be among the first major projects to be finished and one of the boldest architectural statements on the 226-hectare (560-acre) east London site.

Instead it was completed after the 80,000-seat Olympic Stadium, the velodrome, handball arena, basketball arena and the International Broadcast Center.

The aquatics center design was scaled back in an effort to cut spiraling costs even before Britain slumped into recession.

While retaining the sweeping, wave-shaped roof, the size of the venue was reduced to prevent it becoming a white elephant after the games have finished, with two giant wings of temporary seating to be added to accommodate fans during Olympic competition.

"The extraordinary regeneration in east London, all the opportunities, the nation's and region's engagement - I can't look at that Olympic Park without taking pride," Coe said.

Filling venues has not proved to be a problem. In fact, "a world record-breaking demand for any sporting event on the planet" - according to Coe - has provoked anger about the ballot process for tickets.

"Everybody's sort of whipping this up into a bit of a storm but peel the layers back: the problem here is essentially that we had 22 million applications for 6.5 million tickets," Olympics minister Hugh Robertson said. "One in four people are going to be disappointed and there's nothing we can do about that. If we'd built stadia of twice the size, we'd have faced huge international criticism for building white elephants that couldn't be used afterwards ... everybody else around the world thinks this has been one of the greatest successes that the Olympic Games has ever seen."

In a year, successes will be judged for each nation by medals, which will be revealed for the first time on Wednesday.

Britain's challenge now is ensuring its athletes are not burdened by the growing home expectation to match - or surpass - the fourth-place finish in the Beijing medals' table.

"What have we got to get right? It's getting our athletes trained," London mayor Boris Johnson said. "We can't lose to France or Australia! We came fourth last time. We've got to make sure we do better this time and that's going to be tough. That's the missing component for me."

A year from now, Johnson's city will be welcoming 10,500 athletes from more than 200 countries, 5,000 coaches and team officials, 20,000 media personnel and hundreds of thousands of visitors. The 17-day festival will feature athletes competing in 26 sports in more than 300 medal events in 32 venues.