Terrace's pull is the country around it: the Skeena River, Lakelse Lake, Kitselas Canyon, the volcanic landscape of the Nass Valley to the north. In town there is a small museum, a couple of decent parks along the river, and the heritage train station. Allow a half day for the city itself and several days if you want to actually see the region.
Fishing is the dominant outdoor activity — salmon, steelhead, and trout all run the Skeena and its tributaries. Hiking, mountain biking, and (in winter) skiing at Shames Mountain west of town round out the offering.