Magic Mountain is located along the exterior and therefore boasts great views of the lagoon.
The road is quite narrow and steep. I would NOT recommend rent a car and going on your own! Nor hiking: narrow concrete path with cars/ATVs going back and forth…
If I had to choose between Magic Mountain and Belvedere Lookout, I would go for the second one. BL is located toward the center of the island and offers breathtaking views of both Cook's Bay and Opunohu Bay. It had something unique and more magical to me. And… easily accessible by car on normal roads ;)
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.