The first half of Clutha Gold Trail follows the mighty Clutha River through semi-arid, rugged landscapes from the Roxburgh hydro dam to Beaumont. Then it vers east as the landscape mellows until you're in the fertile rolling hills of Lawrence, a quaint historic village where gold was first discovered in New Zealand in 1861.
The trail was recently constructed specifically for mountain biking and walking. It's wide, smooth, easy weather-proof surface is the best of any New Zealand trail. It is a "family-scenic-historic" style ride, generally done over two days. It was built and is looked after by a non-profit trust which charges $25 per rider or $50 per family which also covers the Roxburgh Gorge Trail.
There are plenty of accommodation options along the way and shuttles too. Your best bet for more information is to talk to the good people at the Lawrence Information Centre: http://www.lawrence.co.nz and you should check out the trail website: http://www.cluthagold.co.nz.