It only takes around 2 hours to walk to the top and back down. Rangitoto Island is worth a visit if you like trekking or if you like walking in general haha. It's a very easy walk. But take comfy shoes with grip because the path is made of little pebbly rocks and it can get slippery. Oh and remember to take enough water. There is no water supply (or electricity) on the island.
The ferry can be caught at the ferry terminal in downtown Auckland.
More info on the Fuller's website: http://www.fullers.co.nz/tickets-fares/timetables/rangitoto-island.php
