Kalbarri National Park
Although it is located a considerable distance away from the city. People still manage to go there for a nature retreat and to unwind. It's perfect if you want to disconnect from the hustle and bustle of the city life, and by disconnect I mean cellular reception is not so easy.
It's also a nice venue for treks and fitness goals. You may be require to walk long distances and climb mountains. If you're up for an adventure, this is the place to be.
Photos: All photos are mine
The best one that I've ever been it's the Kruger-Limpopo, in South Africa and Moçambique.