Northwest Queenstown in Mount Aspiring National Park, the Routeburn Track is a 32km route from the headwaters of the Lake Wakatipu southwest over to the Te Anua-Milford Highway (SH94). The Routeburn Track is typically traversed in three days / two nights with stays in the Routeburn Falls Hut and the Lake Mackenzie Hut (reservations required).
In addition to the challenges of tramping in the Southern Alps, there are numerous unbridged stream crossings, and it is typically cold and rainy. And, there are also ferocious mosquitos. The stretch between the huts over Harris Saddle (1,255m) is not recommended for children under 10. Another challenge is logistics -- the road distance is 350km between trailheads.
For an extended hiking trek, the Routeburn Track can be combined with the nearby Greenstone Track and the Caples Track.
To reach the eastern Routeburn Shelter trailhead from Queenstown, head northwest on the Glenorchy-Queenstown Road through Glenorchy. Follow trailhead signage as the sealed road winds its way up valley through the headwaters towards the trailhead. After crossing the Dart River, turn right off the sealed road onto the gravel Routeburn Road leading to the signed trailhead parking area. The total distance from Queenstown to the trailhead is 70km.
To reach the western Divide Trailhead on Te Anau-Milford Highway (SH94) from Te Anau, head north on SH94 for 87km. The Divide Trailhead parking area is clearly marked roadside and has an obvious bus shelter. This trailhead is located 33km southwest of Milford Sound.
If you are interested in dropping out at Hollyfird Camp via the Deadman Track cutoff trail, it can be accessed from Milford Sound by headig south on SH94 for 30km. Then turn left heading north on Hollyford Road for 8.2km.
Note, camping is only permitted adjacent to the Routeburn Flats Hut (15 sites) and the Lake Mackenzie Hut (9 sites).
Overall, Routeburn Track is the 6th most popular hiking trail of all 15 hikes in New Zealand.