From a distance, you could almost mistake it for a designer multi-storey car park. The grey concrete and angular lines are certainly a contrast to the classical marble edifice in whose shadow it stands. Yet the Parthenon seems to look down on the architectural upstart not with disapproval but pride, affection, and most of all hope. Hope that the new offspring can finally bring the ancestral treasures home.
These are heavy expectations for a museum to bear. But the Acropolis Museum was, quite literally, built to shoulder them. Unlike any other museum in the world, it was designed to house something it didn't own. We're talking of course about those infamous marbles that were hacked from the Parthenon by Lord Elgin at the start of the 119th century and that now reside in Bloomsbury in the British Museum. Greece wants them back and having failed to make headway with verbal arguments, it is trying visual ones.
The centrepiece is the museum's roof-top glass gallery. This final floor has been twisted round (rather like the top layer of a Rubik's cube) so that it is in perfect alignment with the Parthenon. The Athens marbles depicting Olympian gods, heroes and animals, have been arranged in the round, replicating the exact layout and dimensions of the original frieze. And glancing out through the floor-to-ceiling windows to the north, you get a real sense of what the whole ensemble must have looked like up on the Acropolis hill back in the fifth century BC.
Contrast this with the London set-up. In the windowless Duveen Gallery, the marbles hang on two walls with the observer sandwiched in between and the flow of the frieze interrupted by heavy doors. What the British Museum does have is quantity – an estimated 60 per cent of the surviving marbles to the Acropolis Museum's 40 per cent. The London exhibits provide copious commentary on this division, from a separate pamphlet detailing the ownership row to detailed captioning for individual portions of the frieze. "A groom wearing a cloak pinned on one shoulder steadies the horse," the explainer for North Frieze XXVII, 72 reads, "The lower part of this figure, together with the foot soldier and driver of the next chariot, is in Athens".
The Acropolis Museum addresses the same issue in a more visceral way, hanging the honey-coloured Greek marbles alongside stark white plaster copies of the British Museum sections. The Greek government of 1840 had to pay to have these copies made, a quarter of a century after the British parliament authorised purchasing the originals from a bankrupt Lord Elgin. Now they are being used to make the case for reunification in the €130m (£110m) museum. This is architecture as argument. Although just in case anyone has missed its message, Greek Culture Minister Antonio Samaras is on hand to hammer it home. "For 200 years, the Parthenon Marbles have been amputated, now they must be reunited. The Parthenon frieze speaks through its totality; this voice should be heard not be silenced," Mr Samaras told guests at a special preview. "This museum is creating huge momentum, a global crescendo. We are winning the fight."
That may be wishful thinking on his part. Admittedly, tempers have cooled since the days when British Museum officials branded attempts to remove the marbles "cultural fascism", comparing them to Hitler's book burning. But it is hard to see any concrete hope today. The British Museum is only sending the deputy chairman of its board of trustees to the official opening. It hardly spells rapprochement. Permanent repatriation is universally acknowledged as a non-starter, and the idea of a temporary loan is a minefield. "In principle, trustees are always happy to consider any loan request, but the borrowing institution would have to recognise our legal ownership," explained the spokeswoman for the British Museum, Hannah Boulton.
That is something the Greek government has repeatedly refused to do; it would legitimise "the deeds of the infamous annihilators", according to Mr Samaras. Some of his museum guides might need a spot more training on this point. "The plaster casts are of the marbles that belong to the British Museum," one guide told his group of invited guests last night, drawing gasps all round. "I mean located," he hastily corrected himself.
At night the interplay of the reflections of marbles and the Parthenon is simply spectacular, and the yearning to see the originals in their entirety overwhelming. But visitors are also (perhaps unintentionally) reminded that British involvement in the saga might not have been entirely dastardly. In amongst the marble and plaster cast montage are gaping expanses of blank wall. They represent the sections of the frieze that no longer survive at all, and some would argue that Lord Elgin in fact saved art that would have otherwise been destroyed. Similarly some of the metopes not taken down from the Parthenon until the 1990s show considerable erosion, often attributed to the high levels of pollution in Athens.
That Greece can look after the marbles properly is no longer in doubt, thanks to the new Acropolis Museum. The primary argument advanced by the British Museum is that keeping the Elgin Marbles in London allows them to be "part of a world museum, where they can be connected to other ancient civilisations".
The idea of a global art is one that resonates with Mary Beard, professor of classics at Cambridge University. "We have a global culture and there's a way in which the division and spread of a monument is a herald to internationalism."
Yet she is swift to add that she understands the Greek pain just as readily. "Imagine the English being told that from now on they could only watch Shakespeare, whose plays incidentally also constitute a global work of art, in Japanese."
You have to feel slightly sorry for Bernard Tschumi, the Swiss architect whose achievement risks being overshadowed by the marbles row. That a new home for the Acropolis treasures is actually finished is not to be skated over. It has been more than 30 years in the planning – that's twice as long as it took the ancient Greeks to build the Parthenon in the first place.
Mr Tschumi won the competition in 2001, and has had to contend with 104 court cases, political infighting, the risk of earthquakes, not to mention the pressure of working in full view of arguably the most influential building in Western civilisation. "I like a challenge," he quips.
He plumped for the same approach as Pei did with the pyramid at the Louvre – an uber-modern building that dialogues with the old. You see this most clearly in his handling of the archaeological remains discovered under the foundations. The museum balances over the excavation site on an irregular forest of concrete columns, a harmonious sharing of the available space between the old and new.
"When you have perfection from the past, how can you imitate it?" Mr Tschumi says. "You have to arrive at another sort of perfection for the 21st century." But what about Bloomsbury's share of the marbles? "I am convinced the marbles will come back," he says. "Until then, the tension and desire are part of the work."
The Elgin Marbles: A troubled history
*Thomas Bruce, 7th Earl of Elgin, pictured below, was the British ambassador to the Ottoman Empire at a time when it included Greece. An art lover, he initially wanted to document the Parthenon, but – with his staff – ended up removing half of the remnants of the building's sculptures.
*Even once he managed to get the pieces out of Athens, his troubles weren't over – many tons were lost overboard and had to be rescued from the sea.
*In 1816 the British government bought the marbles from Elgin – who by then was deeply in debt – for £35,000, and they were given to the British Museum.
*His actions were ridiculed by Lord Byron in his poem "Childe Harold's Pilgrimage".
Should the Elgin Marbles be returned to Greece?
What a difference a day makes. Until yesterday the New Acropolis Museum of Athens had been a closed book to all but a few interested scholars and politicians. But now the first of what will become a flood of variously motivated global visitors were privileged (as I was) to experience the interior as well as the much more problematic exterior of the New Acropolis Museum.
It is designed to remind the world that the Parthenon – both as thing and as idea – cannot begin to be properly understood except in the context of the mighty rock on which it was constructed, and of the vast number of other artefacts, which it also brilliantly displays.
Speaking both museologically, and spiritually, those of us who believe alleged titles to legal ownership to be not just beside the point but wilfully designed to obscure the point, and the true humane goal to be the reunification of all the extant Parthenon Marbles (not only those in the British Museum) in close association with the Acropolis rock, cannot but be hugely cheered by yesterday's inaugural event, a genuine "Athens Spring" (the modern Greek word for which season means literally "opening").
Paul Cartledge is the A G Leventis professor of Greek culture at Cambridge
In 1801 the Acropolis was an Ottoman fortress, its temples turned first into Christian churches, then mosques. The Parthenon itself had been blown up during the last Crusade in 1697, its columns shattered, and most of the sculptures that once decorated it thrown to the ground. The Greeks identified "Greekness" with membership of the Orthodox Church rather than the legacy of Pericles – they were ignoring their ancient ruins, when they were not chopping up the marble remains and burning them in kilns to produce lime. Lord Elgin came along only planning to study the Parthenon sculptures, but when he was presented with the opportunity of saving them, he leapt at the chance. Had Elgin left the Elgin Marbles on the Acropolis, more of the Parthenon sculptures would have been destroyed, as they were decade after decade even following Greek independence. Had Elgin not brought them back to London they would no longer exist.
Modern Greeks like to claim that the Parthenon sculptures are part of Greek heritage. In fact, they are part of the world's heritage, too important to be owned by anyone – and the sculptures can currently be appreciated in half a dozen museums around the world.
Dorothy King is an archaeologist and author of The Elgin Marbles