Natzu is a location from The Legend of Zelda: Oracle of Seasons. It is located roughly in the center of Holodrum, with Goron Mountain and the Temple Remains to the north, North Horon to the west, Eyeglass Lake to the south, and the Moblin's Keep to the east. Interestingly, Natzu's terrain will take one of three different forms, depending on which animal companion Link ends up with.
If Link gets Ricky as a companion, the terrain will be filled with prairie-like greenery and high ledges. Due to the nature of the terrain, Link must use Ricky to navigate much of the area.
If Link gets Dimitri as a companion, the terrain will become filled with waterfalls and swift-moving waters. It is impossible to navigate the area without Dimitri. If Link jumps in the currents without Dimitri, he will be unable to swim against it and will be taken wherever the current leads him.
If Link gets Moosh as a companion, the terrain will become a wasteland. Rocks and long lines of pits will fill the area, making it impossible to traverse without Moosh, even with the help of the Roc's Cape.
It is possible that the name "Natzu" is derived from natsu, the Japanese word for summer.