The Gibbston River Trail runs through the picturesque Gibbston Valley wine region next to the Kawarau River. It’s a mostly flat gravel track that can be walked or mountain-biked, and to be honest biking it would probably be more enjoyable.
It offers nice views of the river in certain spots, which in sunny weather is an intense aqua colour as my pictures demonstrate. But the rest of the time it meanders through somewhat uninspiring vegetation that offers no protection from the sun, and so was a bit of a slog for us in summer. I recommend walking it in sunny winter weather. (In overcast weather the river won’t be such a nice colour.)
Track notes on the DOC website. I’ve rated it as moderate because it’s longish, but you won’t need any special gear for what is essentially a gravel path.