Nature Loop of Picacho Park
The Nature Trail is a short, enjoyable loop near the entrance of the park that is suitable for any level of hiker. The trail is well-marked, there are interpretive signs along the way (more in-depth than 'this a tree, it has spikes'), and the views of Picacho Peak in the background is neat. It also goes right past the Memorial Loop for a short addition and can be easily combined with any of the nearby unmarked trails for a longer outing.
As the trail doesn't really 'start' from a single parking lot (although there is parking near the Memorial Loop that could be used) the most reasonable trailhead is on the corner of the Harrington Loop. This driving loop starts immediately left of the visitor center / pay area, so watch for it before driving too far past the building. If you see the turnoff for the Barrett Loop you've gone too far. Once you park along Harrington head to the southeast corner of the lot and look for a sign for Nature Trail, following the connector trail 175 yards to the start of the loop.
From here turn right (or left, this is a loop hike and it's your life) and start a gradual uphill climb. There are a few large, metal signs along the way, and a marble bench memorial too. A signed fork shows up for the amphitheater, our trail bends left and crosses a shallow wash. After a second wash crossing a more interesting junction shows up, this time the right fork leading over to Calloway Trail, and our trail bends left again and follows the wash northwards. Following the wash is interesting, with some pleasant green growth along the way, though the noise of the highway and view of the ranger housing is a bit jarring.
Before reaching the housing area the trail twists left again and crosses a paved road. Here you could wander off this path a bit, towards the pavilion, and check out the Memorial Loop. This is a very short loop that has colored interpretive signs, an old cannon, and plenty of historical information about Picacho Peak and the civil war. Its a good loop. Nature Trail continues westward and soon meets right back at the cholla tree where you started.
WARNING! Hiking and outdoor related sports can be dangerous. Be responsible and prepare for the trip. Study the area you are entering and plan accordingly. Dress for the current and unexpected weather changes. Take plenty of water. Never go alone. Make an itinerary with your plan(s), route(s), destination(s) and expected return time. Give your itinerary to trusted family and/or friends.