The mighty stone trilithon of Ha'amonga-`A-Maui, looming powerfully above the hungry pigs looking for food in a grassy reserve at the eastern end of the island of Tongatapu, is an extraordinary sight.
How on earth did the ancient Tongans manage to get the two 50-tonne uprights into position? What technique did they use to raise the 30-tonne lintel on top of the uprights where it slots into two slits? And what is it for?
"I think," said Herman Tu'inukuafe, thoughtfully patting one of the huge chunks of coral limestone, "the Tongans a thousand years ago must have been bigger and stronger than the Tongans today."
Hmm, Tongans today seem pretty big and strong to me, but he was certainly right in suggesting that creating the Ha'amonga would have required a heck of a lot of muscle-power.
We had run into Herman while strolling through the empty streets of the capital, Nuku'alofa, on a peaceful Sunday afternoon.
"Hello," he smiled at these obvious foreigners. "How are you enjoying Tonga?" We're having a great time. "Where are you from?" Auckland. "Where in Auckland?" Devonport. "My brother lives there." Not Carl? "Yes. Do you know him?" Small world.
After discovering that link Herman had to take us round the island, including to the Ha'amonga which I had really wanted to see, with some fascinating detours to beautiful beaches, interesting buildings and intriguing villages that you wouldn't get to see on an ordinary tour.
That friendliness and hospitality is typical of what we found in Tonga. Also typical is the fact the origins of the Ha'amonga lie with Tongan royalty.
Just about everything on Tongatapu seems to be linked to the royals who are a tourist attraction in their own right.
"When the cruise ships berth here the Americans especially are thrilled to find there is a king," explained Derek Leonard, a Kiwi who works in the tourist industry. "Having got rid of their own king they seem to be fascinated with any they find elsewhere."
The present royal family also owns many of the most high-profile companies, royals ordered the construction of all the most impressive monuments, ancient and modern, and the new king and his family are the subject of virtually all the interesting stories.
The Ha'amonga, for instance, was built towards the end of the 13th century by the 11th king, Tu'iatui, although there are varying versions of how it was achieved. Legend tells of the stones being carried there by the ubiquitous Polynesian demi-god Maui. But archaeologists talk more prosaically of a workforce of around 1600 being required to haul the stones into position which certainly serves to indicate the power of the king.
Most likely this Tongan Stonehenge was the gateway to the royal compound but it may - according to a theory put forward by the late King Taufa'ahau Tupou IV - have also been used to identify the ritually important shortest and longest days of the year.
Not far away is another stone, against which Tu'iatui used to sit to protect his back, while keeping visitors at a distance by hitting them with a long stick - his name means "king strike knee" - to guard against the risk of assassination.
The present king, George Tupou V, lives mainly in a picturesque wooden palace in the heart of Nuku'alofa, the principal residence for the Tupou line since it was shipped from New Zealand in prefabricated form in 1867, though here visitors are kept at bay with a barbed-wire topped fence rather than a stick.
Although you can't go into the palace grounds we did peer through the red iron gates, decorated with the royal coat-of-arms, in the hope of seeing his majesty.
The cheerful guards explained that the king wasn't at home - in fact he was visiting New Zealand - but we did discover that much of the front of the house, including its distinctive central tower, has been dismantled as part of an upgrade aimed at having the place spick and span for his coronation next August.
Because of the recent death of the old king, the palace and most other public buildings are still decorated with black and purple ribbons.
There are even more impressive decorations at the nearby royal tombs where 11 of the Tupou royalty - including the delightful Queen Salote - are buried.
You're not allowed in there either but it's easy enough to peer over the fence at the enormous coloured banners, wreaths of artificial flowers and fluttering ribbons which decorate the huge white sepulchre with a statue of the late king himself soaring above on a pedestal.
Monarchs from previous royal dynasties are mostly buried in the ancient capital of Mu'a, where their bodies are entombed in enormous stepped pyramid tombs, called langi, made by creating layered platforms of earth held in place by walls of black volcanic stone, with stone crypts in the centre.
Once again the main royal langi is fenced off but there are a couple of dozen others at Mu'a which you can visit, most surrounded by ordinary graves covered with amazing decorations, made with everything from broken bottles and coloured plastic to embroidered mats and woven ribbons.
I didn't expect to find the king at any of the royal tombs but I had hoped to spot him when we went to Sunday morning service at the Centenary Chapel, just up the road from the palace.
This has a special raised pew for the royal family but the only person using it this time was an elderly woman - the Queen Mother, we were told - who arrived with an army escort and two ladies-in-waiting. The singing in the chapel was magnificent, made all the better by the accompaniment from a brass band, making it worth a visit for the music alone.
Afterwards, walking back to the Seaview Lodge, where we were staying, we saw the Queen's car with its distinctive HM plates at the old British High Commission, where she had presumably gone for the traditional Tongan Sunday lunch. This classic example of colonial architecture, complete with a row of canon from the privateer Port-au-Prince, is now home to one of the princesses, the high commission having closed following the transfer of British representation in the Pacific to Suva.
There are several other royal residences around the island including the home of another princess with two white marble cougars guarding the entrance, the French-style chateau built by the new king when he was crown prince and the picturesque Kauvai Royal estate sitting in grounds filled with lush tropical plants on the shores of a lagoon.
Most of the other sights around Tongatapu also have royal associations. For instance, the small cairn marking the spot where in 1777 Captain James Cook had a nap emphasises the fact that he was on his way to visit the "sacred king" (unfortunately I didn't get to see the landing site of Abel Tasman in 1643 which is at the other end of the island).
The flying foxes at Kolovai, said to have been introduced as a gift from a Samoan maiden, can only be hunted by the royal family. Most of them have recently moved closer to the improved food supplies around Nuku'alofa, prompting me to ask whether ordinary people could hunt them there. "Oh no," said our guide, Josephina, "I don't think anyone eats them now." "I do," I said, causing some consternation, until I added, "I ate flying fox in Vanuatu."
The amazing blowholes which run along a 5km stretch of the southwest coast, in favourable weather providing a line of hundreds of plumes stretching as far as the eye can see, are called Mapu `a Vaea, "the chief's whistle", a possible reference to a king who used to summon his warriors by blowing a whistle.
The old Vanu Wharf, once the island's main wharf and later used as a diving platform by local youngsters until it was shattered by a cyclone, has been replaced by the new Queen Salote Wharf further east.
Even last year's riots that razed much of the town centre - you can now wander over huge concrete and tile floors which once sat under a department store, a hotel, a shopping arcade and the island power company - seem to have specifically targeted companies owned by the then crown prince (as well as the prime minister and the Chinese community).
But, despite visiting all those places with royal associations, I had failed to catch a glimpse of the monarch, so on my last day on Tongatapu I thought I might try the Nuku'alofa Club, a gentlemen's club founded in 1914 by a previous monarch to provide somewhere for Palangi diplomats to drink, which still has the king as its patron.
A few years ago it opened its doors to Tongans - though not to women - and is the haunt not only of local business people but of nobles and royals.
I had envisaged something like Auckland's Northern Club, with dark panelling, deep leather seats, lush drapes and thick carpets, but the reality was a little different, with a decor reminiscent of a Kiwi pub in the 1970s or, as my host put it, "like a public bar in Mangere."
The new king wasn't there - though there were a few nobles and minor royals - but his beer was ... and it's named after me!
The local brew, which I found extremely tasty, turns out to be produced by the Royal Beer Company, which the then crown prince started in 1987 in a joint venture with a Swedish brewer, and its premium brand is called Ikale after the local variety of eagle.
So, while I might not have met the king, I definitely feel as though I've shared a beer with him.
*Jim Eagles visited Tonga with help from Air New Zealand and the Tonga Visitors Bureau.