Walking

 Go for a long hike for whatever duration takes your fancy. A great opportunity to get outside in nature (or explore different parts of your city) while building up your fitness and endurance. Perfect for beginners who are just getting started and more advanced athletes who want an easier cardio session. To ramp up the challenge attack any hills, slopes or gradients you comes across at a fast pace. Alternatively start inserting short bursts of easy running into your walks. When you tire simply shift back to walking. Great for building up your leg strength and preparing your body for the tougher run and sprint intervals ahead.