Run stairs. Find a set of stairs that are not too steep and that are 30 or more steps high. Start off by running up one flight of stairs, then walk down one. Next, run up two flights and walk down one. Finally, run up three flights and walk down one, completing the circuit. Complete the whole circuit as many times as possible in 20 minutes.
If you are having a hard time finding stairs, check the local high school stadium or local sports field. Bleachers are great for this work out.
If you find yourself unsteady, use the handrail just to be safe.
Make sure there are no other people on the stairs. You don't want to hit them and it will also make you unstable.
This is a great cardio exercise as well as beneficial for your legs. The more your heart rate is up, the more fat and calories you will burn. Do this exercise for longer periods of time to increase intensity and burn more calories.