It's one of the most gruelling races on the planet - so tough that only four people have ever finished it.

The Revenant ultra adventure run gets underway at Welcome Rock on Blackmore Station in Southland tomorrow (19 Jan).

With a total race distance of 200 kilometres and over 16,000 metres of vertical ascent, and tricky terrain, competitors must complete four laps of the course within 60 hours with no outside help.

Race director Scott Worthington has been readying the course and joins Anna to tell her all about what's ahead for the 40 or so runners taking part from NZ and around the world.

CLICK HERE to listen.

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