A viewpoint into Cirque de Mafate which can be reached by car is Piton Maido. It directly overlooks the cirque and you can see places like Marla, Trois Roches, Roche Plate and La Nouvelle. It's a very bizarre landscape and absolutely breathtaking.
To get to the viewpoint, always follow the forest road no. 8 (RF8) to its end where you park your car at an elevation of 2190 m. Make sure to start early in the morning because the clouds already move in before noon. From St. Leu which is at the west coast, it took us about 2 hours to get to Piton Maido.