London (CNN) -- July 27 marks the start of the final countdown for London's staging of the 2012 Olympic Games.
One year from now, 14,700 competitors from 205 nations across the globe will take part in the opening ceremony. An estimated one billion people tuned in to watch Beijing's glittering extravaganza in 2008, and this time the eyes of the world will be on the British capital.
Despite fears that the venues would not be ready on time, that the city's creaking infrastructure would not be capable of dealing with such an influx of visitors, it appears that London is on track to deliver.
The International Olympic Committee has already given an interim thumbs up, with most venues at an advanced stage of completion.
But it has been a bumpy path since 2005, when it became the first city to be awarded the world's biggest sporting extravaganza three times in the modern era, previously having the honor in 1908 and 1948.
Costs have rocketed, local councils cried foul when the marathon route was moved from their borders despite earlier promises, and the vagaries of the ticketing system have left many people upset that they will not be able to participate.
With that in mind, CNN takes a look at some of main issues surrounding London 2012.
The projected cost of the 2012 Olympics ballooned from the initial bid estimate of £4 billion ($6.5 billion) to £9.3 billion ($15.2 billion) in 2007.
The London Organizing Committee for both the Olympics and Paralympics has a budget of £2 billion, which it says will be mostly funded by the private sector.
However, the public sector will foot most of the overall bill -- though the budget was not protected from the wide-ranging spending cuts implemented by the coalition government since 2010, losing £27 million ($44 million) that year.
On the other hand, with many events already sold out, organizers are well on the way to achieving their target of £500 million ($820 million) revenue from ticket sales.
With more than 20 million applications for 6.6 million tickets available for 39 sporting disciplines in the UK allocation alone, it was no surprise that many people were left unhappy.
It turned out that more people missed out in the initial ballot than were successful, with most events -- especially glamour dates such as the men's 100-meters final and opening/closing ceremonies -- being massively oversubscribed.
The Guardian newspaper reported that only 30,000 of the 80,000 seats available for that 100m race were on offer to the British public anyway -- 1.3 million applied.
But one of the main criticisms was a system that meant money was taken out of your bank account before you knew what you had been allocated, the details of which which you found out up to a month later.
This was one of London's weakest areas, according to inspectors from the International Olympic Committee. With an underground train system in part dating back to the 1860s, most of the city's commuters would agree.
The Jubilee line, one of the more recent additions on the network, has been upgraded to suit its role as the main tube route to Stratford. The Olympic Javelin service, a high-speed rail link from St. Pancras International in central London, is expected to take 25,000 passengers an hour to the Olympic Park.
However, critics fear that the volume of travelers will seize up London's overcrowded transport system, especially at rush hour. Businesses have already been warned to put in place contingency plans for getting employees to work.
For those hoping to drive to the Olympic Park, there are two park-and-ride sites outside London which will connect with the Javelin service. People willing to walk or cycle can navigate 75 kilometers of upgraded routes in the region.
The day after London was awarded the 2012 Olympics, the capital was rocked by bomb blasts which killed 52 train and bus commuters, injuring more than 700. While the so-called "7/7" attacks were not proved to be linked to the IOC's decision, it brought home how the city might be targeted during the Games.
Organizers have worked with the government, police and other essential support services to put in place measures to prevent any repeat of that dark day.
"We have a robust safety and security strategy," Home Secretary Theresa May said this month when announcing a set of exercises to simulate possible problem scenarios.
"The testing of our plans, structures and responses to ensure they can deal with any incident is vital. It is important we learn lessons ahead of the Games."
London 2012 will be a mixture of old and new. A 2.5 square-kilometer area of industrial wasteland in the eastern borough of Stratford is being regenerated to form the new Olympic Park.
It houses the main Olympic Stadium, where the opening and closing ceremonies take place along with the track and field events. Also on the site are the aquatics center and arenas for basketball, hockey, cycling, water polo, handball, BMX and wheelchair tennis.
Visitors can experience iconic London landmarks, with several events starting and finishing at The Mall near Buckingham Palace, beach volleyball at Horse Guards' Parade near No. 10 Downing St, a cycling time-trial at Hampton Court Palace, triathlon in Hyde Park and equestrian events in historic Greenwich.
The new Wembley Stadium will host men's and women's football, Wimbledon will again welcome the world's top tennis players and Lord's -- the home of cricket -- stages archery.
Watersports such as sailing, rowing and canoeing will be held outside London, as will some football matches.
After the closing ceremony on August 12, organizers will begin the process of transforming the Olympic site into what they say will be one of the largest urban parks created in Europe for 150 years.
While that move has been welcomed by environmentalists, the decision over the future of the Olympic Stadium has been more controversial.
Football club West Ham United will move into the venue on the basis that it will still be used for athletics events, much to the anger of north London-based rivals Tottenham -- who had planned to use the site for a new purpose-built stadium.
Leyton Orient, the team actually located closest to the ground, sought to block West Ham's application on the grounds that it would destroy the third division club's fanbase.
Organizers have been proud to announce that one goal has already been achieved a year early, with the International Inspiration program reaching 12 million children in 17 countries worldwide.
In flood-prone Bangladesh, where thousands of children drown each year, it has helped teach 80,000 non-swimmers to survive. In Trinidad & Tobago, it is using sport to address the issue of violence, and in Zambia it is providing education about HIV and AIDS.