Wow. It’s huge.

Proposed during the halcyon optimism of the bubble era and constructed during a period of economic slowdown almost a generation later, the National Art Center, Tokyo has finally opened and is positioned to be the jewel in the crown of the Japanese government’s quintet of national museums.

Designed by architect Kisho Kurokawa, 72, a founder of the free-form and avant-garde Metabolist movement of the 1960s, the 35-billion-yen NAC features an enormous, gently rippling facade made of glass panels. The atrium, which stretches the length of the building, is a wide, accommodating swath with 22 meter ceilings. A couple of restaurants and bars perch atop massive, inverted conical concrete constructions, behind which are stacked, with the space efficiency of a coin-locker system, 12 exhibition halls comprising a total floor space of 14,000 sq. meters, making this easily the largest art space in the country.

The NAC’s inaugural exhibition is “Living in the Material World — ‘Things’ in Art of the 20th Century and Beyond.” More than 500 works in all imaginable media are on display, which, remarkably, occupy less than half of the NAC’s available exhibition space. Yet it still leaves the visitor exhausted.

Who cares if there isn’t a unifying theme — this is a show with something for everyone. Borrowing from the collections of Japan’s national and prefectural museums, and a number of leading private, corporate and overseas collections, “Things” looks at Japanese and foreign — mostly Western — art from the last hundred years or so. Allow yourself several hours for a total art-gorge, and be prepared to deal with crowds — but by all means get out and see this one.

That’s the good news. Now, at the risk of sounding like a party pooper, it’s necessary to address a couple of things. First, there is a certain irony that the NAC has opened with an exhibition celebrating “things,” when in fact it doesn’t actually have any. Yes, this is an art museum without a collection.

Although the NAC’s official name, Kokuritsu Shin-Bijutsukan, properly translates as New National Museum, there are inconsistencies in its English-language materials. The Web site uses the term “art exhibition facility” while the catalog contains this doublespeak gem: “As long as a museum possesses actual space in the real world, then it will remain a place where people can discover ‘things’ and it is through this coming together of people and things that new culture and art is born.”

I think a more accurate explanation would read something like this: “As inclined as the Japanese government is to spend money on public works projects such as this big beautiful building, they are just as disinclined to spend money on works of art.”

Which is not to say that there will not be good exhibitions at the NAC. The next show, scheduled to begin Feb. 7, is being organized in conjunction with the Centre Pompidou and will look at expatriate artists in Paris from 1900-2005. Some 200 works by the likes of Picasso, Modigliani and Foujita will be on display, drawn from the Pompidou. But its as if the NAC is saying, “Thanks Centre Pompidou, so nice of you to share your art. We would return the favor, but cultural sponging works better for us. Sorry.”

My second issue: Even the Pompidou show will occupy but a fraction of the NAC’s total wall space. So, what can you expect to find in the other 10 rooms? Believe it or not the answer is vanity shows, featuring work from amateur art associations.

There are literally hundreds of these groups in Japan, most rigidly hierarchical with the elders acting as teachers in traditional-style painting. Everyone else pays hefty membership fees, and, in exchange for the right to participate in occasional exhibitions, are expected to peddle admission tickets to family and friends.

Long-accustomed to showing on pegboard walls in community centers, these dilettantes will now move into the most advanced art exhibition space in the country — they have already rented the majority of the NAC’s exhibition space through the end of 2008. Take that, curators!

The new NAC is a terrific exhibition space. Indirect fluorescent lights are complemented by focusable halogen spots, the ceilings are sufficiently high to accommodate large-scale works but not so high as to leave the rooms feeling cold and impersonal. Each and every wall is movable, allowing endless configuration possibilities. There will be good and great shows here, to be sure. And honestly, I can half accept the decision to forgo a collection. But only the most gormless of bureaucrats could have made the decision to turn over 10 of the center’s 12 galleries to weekend watercolorists.

I’m reminded of the old parable that presumes to differentiate the optimist from the cynic by asking whether a glass appears half empty or half full. I want to be an optimist, so I’ll focus on the two rooms of this world-class exhibition space which will be used for world-class art, and endeavor to see the glass as half — well, make that one-sixth — full.