New Zealand, especially the South Island the scenery is so diverse. To see the South Island properly you would need nearly a month.
The best way to see the SI is to start at Christchurch, travel north to Kiakoura, go whale watching, can also see many seal colony's along the coast.
Then to Blenhiem and the Marlborough Sounds, visit the wineries, Picton, over to Nelson, if have a chance goto Tahaka, Collingwood, some magnificent coastal scenery.
Down through the Upper Buller Gorge, and this point, its very confusing in which way to go, goto Westport and down to Greymouth, visiting the Pancake Rocks on the way (pray for bad weather so the blowholes are roaring). I would stay here for a few days then travel upto Reefton, very old gold and coal mining town, can still see some of the old mines. Explore around the area.
Goto Shantytown, a replica tourist site which looks at the early West Coast, goto Kumara, and see where the Chinese mined for gold over 150 years ago, visit the lakes Moana and Brunner.
A must is to visit Arthurs Pass, fantastic scenery, I used to travel from Greymouth to Christchurch for a days drive just for the scenery.
Down to Hokitika, visit the greenstone factories, then further south to Hari Hari, Whataroa and you step back into the past, in some places. There are still pubs here that were built over 120 years ago, with lots of history.
Down to Franz and Fox Glacier, stopping at Lake Matheson, plenty of detours here to see history at Bruce Bay, Knights Point, then on to Haast.
Then to Central Otago, Wanaka, Queenstown, Milford Sound, to Dunedin, Invercargill, then upto Christchurch.
Some detours here would be to see the Waitaki River and the hydroelectric dams and the lakes made by these dams. My Grandfather, Father and Uncles worked on these dams in the 60's and 70's.
Dunedin is so diverse, you can still see the old castles on the hills that protect the city, the scottish settled here.
As you can see the South Island is so diverse, a little of everything for everyone.
So if you plan to go back again, think about what you want to see and also Wiki the South Island.
The pictures bring back alot of memories and yes I am biased for the West Coast, Greymouth, as I lived there for 15 years.
Cheers ...