On a drive from Blenheim to Nelson on State Highway 5, save plenty of time for Pelorus Bridge. It is a very pretty area with several tracks, some remnant native forest and forest regrowth, and an interesting historic bridge. The bridge provides access to Te Hoiere Pelorus River and Te Araroa, as well as a cafe and campground.
The walking and hiking options range from short loop tracks on either side of the river (about 30 minutes or so) and a longer loop track up to trig K (up to 4 hours). The trig sits at the top of the 417 metre hill behind the carpark.
If you are very short of time, walk out onto the bridge on the footpath on the west side for the view up the river gorge. Try not to worry about the earthquake effect every time a truck goes by! Where you access the bridge, there are also some steps down to the rocks beside the river.
