The Routeburn Track is one of New Zealand’s classic multi-day tramps. Walking through the Mt Aspiring portion of the walk as far as Routeburn Flats makes for an excellent day hike of moderate difficulty. The track follows the Routeburn through beech forest as it tumbles down from the flats, and there are views through the trees of the burn and high peaks along the way. When you get to the flats the scenery opens up to provide uninterrupted views of the Humboldt Mountains, and Flats Hut makes is a good spot for lunch before heading back the way you came.
If this is not enough scenery or exercise for you then continue on to Harris Saddle and Conical Hill for even better views. That will be a long day walk but totally worth it. There’s information for the whole walk on the DOC website. You can also take a side trip from the Flats Hut up the Routeburn North Branch, which is a very picturesque valley indeed.
Routeburn Track to Routeburn Flats: The Scenery