For the most part, the Phoenix metro area is relatively flat with little elevation change noticeable when you drive around from city to city. Know as the Valley of the Sun, we are surrounded by mountains which make for some beautiful, scenic hikes.
I live in the East Valley town of Gilbert sandwiched in between, Chandler, Queen Creek and Mesa so to get out of the city scape and into nature, the closest place to hike is at the San Tan Mountain Regional Park. This 10,000 acre part of the Sonoran Desert has about 8 miles of trails within the park. A favorite and easy trail to follow would be the Moonlight Trail which is well groomed with no steep inclines where you can take in the unique desert landscape and get up close to the magnificent Saguaro Cactus which can grow up to 40' tall. Fun fact, the Saguaro Cactus flower, when in bloom, was selected as Arizona's State flower back in 1931. For the more adventurous hikers out there, there are trails that will take you up where the eagles soar and offer views looking North of the East Valley over Queen Creek towards Apache Junction and to the other popular hiking destination, Superstition Mountain.
The Superstition Mountains offer a wide variety of hiking options and is a popular destination for serious outdoor enthusiast. Its worth noting that the Superstitions are only open to hikers and horse riding. No motorized vehicles or bicycles are permitted in the park. Notable trails are Hieroglyphic Trail, Wave Cave Trail which delivers what the name suggests, Weavers Needle Loop, Three Sisters Summit and Flatiron via Siphon Draw Trail. With the Superstitions being located in the East of the Phoenix Valley, the views from the top of Flat Iron looking West are nothing short of breath taking looking over the valley floor stretching out for miles into the distance.
There are some great online resources if you are planning an outdoor stroll to experience either of the two mountains mentioned above (Links below to Alltrails.com). Both are easily accessible if you live the the Phoenix East Valley and have hikes ranging from easy to hard. This is the valley of the Sun, wear the appropriate footwear, take a hat, stay hydrated, and finally, don't stand on or pick anything that rattles. Rattle Snakes live in these areas and become active in Spring when the sun comes out to warm them up. This fact is not as scary as it sounds as snakes keep to themselves and will slither off to keep away from humans. Should you encounter one, as obvious as it sounds, stay away from it. The people who are dumb enough to try and pick one up are usually the ones who get bit and end up with a large hospital bill. Keeping pets on a leash is also well advised.
Hiking is a great way to stay active, get some fresh air and enjoy nature.