The turn-off to the main eastern entrance of the huge Tararua Forest Park is just south of Masterton on SH2; follow Norfolk Rd about 15km to the gates. Mountain streams dart through virgin forest in this area, known as Holdsworth, which also features swimming holes, picnic spots and campsites (adult/child $20/10). Another popular section is the Waiohine Gorge, although it's reached by a narrow, unsealed road; look for the turn-off south of Carterton.
Heading into the hills, walks include short family hikes, excellent one- or two-day hikes, and longer, challenging hikes for experienced bush-bods (west through to Ōtaki Forks). Check weather and track updates and hut/camping access before setting off, tell someone where you're going and when you'll be back, and be prepared to be baked, battered and buffeted by fickle conditions – exciting!