Yoga improves flexibility, posture and blood flow. Through the breathing exercises involved with the exercise, your respiratory system is strengthened, you have deeper, more restful sleep and you have MORE energy after your practice, no caffeine required!
It is also proven to decrease stress and anxiety, and increase your concentration and memory!
If that hasn't impressed you enough, yoga just looks ridiculously cool. It isn't just downward dog and tree pose, there are so many different poses and types of yoga to experience. Ranging from high energy flow classes (Bikram, power or Vinyasa yoga) to slow, lengthening poses with relaxing breathing techniques (something like Hatha or Iyengar yoga). For the more adventurous there is even partner yoga or antigravity yoga, where all poses are preformed off the floor!
Living in Sydney, It is almost guaranteed that there is a yoga studio near you, commonly with a wide range of styles to choose from. Check out this website to find your closest studio.
I personally recommend the Power Living studios, located in Bondi Junction, Manly and Neutral Bay. The very experienced and friendly teachers will have you bending in ways you didn't know were possible within a couple of visits, all whilst providing you with a very hardcore workout.