The Auckland War Memorial Musuem to give it its full name, is one of the major sights in Auckland and really worth making the effort to visit.
The builing itself is beautiful and set in the green fields of the Domain. Inside, the musuem has a variety of New Zealand/Pacific cultural displays. The Pacific masks and spirit figures are seriously freaky.
The Maori cultural show costs a bit extra but is worth seeing. They demonstrate traditional songs, dances and fighting and the group sticks around afterwards to explain the Maori exhibits and answer questions. Maori culture is an integral part of New Zealand and the displays help you understand some of its aspects.
The War memorial exhibit on the top floor is moving, demonstrating the involvement of the Kiwi troups in the World Wars. And check out any temporary exhibitions, you never know what they may have. I saw the 'Body Art' exhibition, all about piercing, tattooing, scarfication, corsetry .... interesting, very interesting.
The musuem's cafe does good food and if you visit on a nice day take a wander around the Domain before you leave. There's a sculpture garden, fragrance garden and the Winter Gardens (two giant conservatories) are quite impressive. The Fern garden is pretty dark and shady, a good place to rest on a hot summer's day. And if you time your visit right, catch a free summer concert in the bandstand on Sunday afternoons.