Manawatu Gorge is a spectacular geographical structure formed thousands years ago by the Manawatu River, the main river in Manawatu-Wanganui region. Manawatu Gorge is only 15-20 minute drive from Palmerston North city. The gorge is popular with jet-boaters, kayakers, walkers and campers (credit to DK Eyewitness Travel New Zealand & wiki). Shuttles from Palmy to the gorge (vice versa) are available from the Palmy I-Site in summer.
The most popular walking track is the Manawatu Gorge Track, a 10.1 km or 3-5 hour track one way, from Manawatu Gorge East to West (or West to East). My classmates and I did the East to West track in late autumn 2014 so it was pretty cold. The following year, my friend and I did the opposite (West to East) in early summer.