Today I hope you found some outdoor stairs to tackle (or a hill) to incorporate into your walk. Besides focusing on improving cardio this also helps build your core muscles.
Finding it hard to know if you are getting in a 3-5km walk. Try using Googlemaps to measure out a route in your neighbourhood or use a pedometer device like a Fitbit or an app on your phone. Personally my fitbit keeps me motivated but, I also often like to map out a loop around a pond or through a park to give me a destination to reach.
Did anyone join you on your walk today? Toby was my walking partner.