Waitakere Ranges Regional Park is a large bush park at 300 Scenic Drive in Nihotupu, Auckland, with a Google rating of 4.8 from 177 reviews. Its listing describes native rainforest, waterfall walks and surfing off black sand beaches, and reviewers mention Lion Rock above Piha beach.
A regional park like this is best enjoyed by matching the walk to your fitness and the time you have. Bush tracks can run longer than the signs suggest, so carry water, wear sturdy shoes and tell someone your plans. Beaches on the west coast can be windy with strong surf, so check conditions and swim between the flags. Many visitors start early, when the bush is quieter and the car parks have more room.
For a rainforest walk or a black sand beach day from Auckland, it is a highly rated place to begin.