Te Wahipounamu is the Maori word for what is the fjordlands area in the southwest corner of the South Island of New Zealand. This includes the famous Milford and Doubtful Sounds.
I did a tour of Milford Sound and had the pleasure of going immediately after it had rained for 24-hours. Water was flowing down the sides of the fjord in hundreds of small waterfalls, and the large waterfalls were going at full flow.
Visiting can usually be done on a day trip from Queenstown, but you can also stay in the region to do and experience more.