Amid the tumbledown columns and olive groves of the ancient stadium in Olympia, the high priestess holds the torch high at the lighting ceremony. 
The flame was lit in the ruins of the 2,600-year-old Temple of Hera, where actors used a concave mirror to harness the sun's rays. 
The Liverpool-born swimmer handed the torch to 19-year-old British boxer Alexander Loukos. 
Loukos grew up in east London, where the Olympic Stadium is situated, but his father hails from Greece. Making its way to Britain, the flame will first take in Greek archaeological sites including the Acropolis and Olympic Stadium in Athens, site of the first modern Games in 1896. - Actors dressed in ancient Greek costumes light the Olympic torch at original stadium
- Solemn ceremony marks the start of flame's week-long journey to Britain
- Torch will be carried by 8,000 relay runners and cover 8,000 miles across UK
- First runner is Greece's champion swimmer Spyros Gianniotis
(CNN) -- Thousands of years after the first athletes competed at the ancient stadium in Greece, a high priestess swathed in white lit a flame from the sun to mark the start of a new Olympiad on Thursday.
The Olympics are as much about tradition and legacy as they are sporting events, with none so vivid as the lighting of the torch which will now wind its way from Olympia to the Games in London.
The solemn ceremony, held in the ruins of the 2,600-year-old Temple of Hera, saw actors in ancient Greek costume use a mirror to harness the sun's rays and light the Olympic torch.
It marks the start of the flame's week-long journey to Britain, where it will begin an 8,000-mile (12,875-kilometer) route across the country before entering at the new stadium in east London.
Olympic torch relay begins in Greece 
Nine-year-old schoolgirl Niamh Clarke-Willis makes history as she presses the button to officially open the Olympic stadium along with London 2012 chairman Sebastian Coe. They were joined on stage by TV presenters Gabby Logan and Vernon Kay. 
Paralympic gold medalist archer Danielle Brown also took part in the ceremony. The opening weekend included the British Universities and Colleges Sports Outdoor Championships, the first athletics meeting at the 80,000-seater stadium. 
Brown fired arrows into a spinning target, covered with the names of 100 children in the crowd -- and Clarke-Willis was the lucky winner. 
Logan looks on as her husband Kenny, a former rugby union international, competes in a celebrity tug-of-war. About 40,000 spectators watched entertainers including impressionist Jon Culshaw, actor Hugh Bonneville, former Spice Girl Melanie C, rapper Chipmunk and comedian Jack Whitehall. 
Wet weather didn't stop thousands of visitors turning up. The venue was built using 10,000 tons of steel, considerably less than other Olympic stadiums organizers say, and with an emphasis on sustainability. Construction began in May 2008 and was completed in March 2011. 
James Ellington, left, celebrates winning the men's 100 meters final during the weekend's BUCS VISA Athletics Championships, one of the Olympic test events. 
Katy Sealy throws in the javelin event. The track and field competition was watched by a reported crowd of around 6,000 during the day before numbers swelled for the evening show. 
It was the first time many visitors had walked around the Olympic grounds, including the new aquatics center. They appeared cautiously optimistic about the site, with one family telling CNN the seats were comfortable but there was a lack of rubbish bins. 
Visitors had to queue for events as they passed through airport-style checks. Security was high at the event, with police helicopters fyling overhead and armed officers patrolling the grounds. London 2012 Olympic stadium opens 
More than 250 Guardsmen mark 100 days until the London 2012 Olympics starts on on July 27. They are at Horse Guards Parade in central London, which will host beach volleyball. 
China, which hosted the previous Olympics in 2008, also marked the milestone as athletes performed outside the Bird's Nest stadium in Beijing. 
Melissa Wu, a diving silver medallist four years ago, poses with Australia's Boxing Kangaroo Olympic mascot as the 100-day landmark is celebrated in Sydney. 
The future of London's new Olympic stadium is one of the unresolved issues surrounding the Games' legacy. 
Olympic mascots Wenlock and Mandeville strike a pose outside the London 2012 store at Heathrow Airport. 
Giant Olympic rings are towed on the River Thames in front of the city's iconic Tower of London on February 28, 2012. 
The Arcelor Mittal Orbit viewing platform seen next to the Olympic stadium. World-renowned sculptor Anish Kapoor designed the skyscraping sculpture that stands at 115 meters high. 
London 2012 Olympic Torchbearers Dinah Gould and Dominic John MacGowan pose with Mayor of London Boris Johnson on March 19, 2012. 
The Duchess of Cambridge, Kate Middleton, meets Great Britain's Hockey Team at London's Olympic Park on March 15, 2012. 
Members of the emergency services take part in a London Olympics security drill entitled Exercise Forward Defensive on February 22, 2012. The exercise was to test responses to a possible terrorist incident during the Games. 
British rowing legend Matthew Pinsent helps lift in the first of 16,000 beds to be installed in London's Olympic Village on January 26, 2012. 
Analyst Jignasha Patel prepares a sample for testing in the anti-doping laboratory which will test athletes' samples from the London 2012 Games on January 19, 2012. 
Workers carry out the installation of artist Monica Bonvicini's "RUN'"sculpture in the plaza of the London 2012 Handball Arena at the Olympic Park on January 12, 2012. 
Models wear the Volunteers Uniform for London 2012 at a photocall at the Olympic Park on November 22, 2011. 
Organizers expect 80% of the eight million ticket-holders to use the various rail systems, including the tube, during the Games. There will also be an Olympic Route Network where road traffic will be shut off to allow 55,000 athletes, officials and media to get to venues each day. 
London 2012 Olympics: 100 days to go Taking center stage in the lighting ceremony was Greek actress Ino Menegaki as the traditional high priestess. Among the dignitaries present were International Olympic Committee president Jacques Rogge and London organizing committee chairman Sebastian Coe.
The first relay runner to take the flame was Greece's Liverpool-born open water swimming champion Spyros Gianniotis.
He then passed it to 19-year-old British boxer Alexander Loukos, who grew up in east London where the Olympic Stadium is now situated, but whose father hails from Greece.
Making its way to Britain, the flame will first take in Greek archaeological sites including the Acropolis and Olympic Stadium in Athens, site of the first modern Games in 1896.
Arriving on May 19 at Land's End in the far southwest of England, it will then wind its way through 1,019 communities, carried by 8,000 torch-bearers.
The final leg will run from Hampton Court Palace, the former home of King Henry VIII, before arriving at the opening ceremony on July 27.
The flame will burn until the Games end on August 12 -- a tradition that was revived at the 1936 Berlin Olympics.
