Above the entrance to the passageway there is an opening called a roof-box.
This was created to allow sunlight to penetrate the chamber on the shortest days of the year, around December 21.
At dawn, from December 19-23, a beam of sunlight bursts into the roof-box and reaches the floor, gradually extending 19m to the rear of the mound.
As the sun rises higher, the beam widens so the whole room becomes dramatically illuminated. This event lasts for 17 minutes, beginning at about 9am.
Standing with my back pressed to a wall inside this 13.5m-high structure, it was hard not to try to transport myself back to a time when Stone Age astronomers harnessed the sun.
"Above you is about 200,000 tonnes of loose rock which is holding all this together," the Newgrange guide told our tour party, with a touch of Irish mischief. "But don't worry folks, it won't fall down ... remember the Irish are world famous for being builders."
The accuracy of Newgrange as a time-telling device is astonishing when you consider it was built about 3200BC - 500 years before the Great Pyramid of Giza and more than 1000 years before Stonehenge.
One theory is the ancients designed it as a pathway to the gods, so the dead could follow the beam of light directly to the sun.
The mind-boggling site at Newgrange was one of a number of surprising highlights of a two-day visit to Belfast in Northern Ireland before continuing south to the international tourism Mecca of Dublin.
I arrived in Belfast from Glasgow on a short-hop domestic flight after travelling from Auckland.
The stylish Malmaison Hotel near the heart of Belfast's CBD proved the perfect base to explore the city, which has undergone a remarkable transformation in recent times.
Belfast is keen to play down its troubled past, while at the same time acknowledging that the violent sectarian conflict that once raged between its Catholic and Protestant populations is part of its rich and varied history.
At the height of the industrial revolution, Belfast was the global epicentre of the Irish linen industry, tobacco production, rope making and shipbuilding. Today, it is morphing into a resurgent, dynamic capital that boasts emerging quarters, diverse charms and hidden secrets.
The Cathedral Quarter is the oldest part of town and has lively pubs, clubs, restaurants and hotels to suit every budget.
Belfast is also proud of its musical heritage and has colourful and beautifully crafted street murals celebrating famous sons such as the incomparable Van Morrison, punk rock heroes Stiff Little Fingers and the late Gary Moore, guitarist for 70s chart-toppers Thin Lizzy.
It is an easy area to explore on foot and in-between listening to any number of live bands and singers at the vibrant and packed pubs, top eating spots include Hadskis in Donegall St and Deanes Meat Locker in the heart of the city.
Belfast's architecture is also well worth exploring.
The City Hall in the Linen Quarter was completed in 1906.
It was constructed to reflect Belfast's city status, which was granted by Queen Victoria in 1888. The rich interior includes notable features such as the Grand Staircase, the Reception Room and the Great Hall.
And the impressive Linen Hall Library in Donegall Square North is also worth a look. It was founded in 1788 and is steeped in local history.
But if you want to mingle with the friendly locals, head for the bustling St George's Market, one of Belfast's oldest attractions. Built between 1890 and 1896, St George's was named Britain's Best Large Indoor Market 2014 by the National Association of British Market Authorities.
Open Friday, Saturday and Sunday, it offers a huge range of local, continental and speciality foods including meat and fish, cheese, coffee beans, tapas and organic products.
But the biggest attraction in town is the spectacular Titanic Belfast experience. It is Northern Ireland tourism's runaway success story.
Built at the cost of nearly $200 million and opened in 2012, Titanic Belfast relates the story of the famously doomed ocean liner that was constructed at the local Harland & Wolff shipyards.
The state-of-the-art building is shaped like the bows of a ship and comprises nine galleries over four floors.
Titanic Belfast transports you through time: travelling from Edwardian "Boomtown Belfast" - learning about the lives of the workers who built the ship and the lives of the passengers and crew who made the fateful voyage - to the present day.
There is even live streaming from where the wreck has lain at rest on the North Atlantic Ocean floor since it struck an iceberg and sank in April 1912 on its maiden voyage from Southampton to New York.
With the established delights of cosmopolitan Dublin just a short drive south, Belfast offers a great second option for a thrilling two-city break to magical and historic Ireland.
CHECKLIST
Getting there
Emirates flies daily between Auckland and Dublin with direct connections each way in Dubai. Fares start from $2067 for Economy Class return.
Online
ireland.com
