Hidden Valley Trail via Mormon Trail is a 2-4 mile hike, depending on the route you choose to take and how much additional exploring you do. This hike offers a natural rock tunnel, petroglyphs, dry waterfalls, Fatman's Pass, and views of South Mountain. This hike can be done year round, but is best enjoyed in the Fall and Winter months to avoid to hot,  Arizona sun. 

The trail is primarily flat, most of your elevation gain happens in the first mile of the hike, after that it levels out.  At about 1.1 miles you'll  come to the intersection with the Mormon Loop trail, which is marked and heads off to your left. Don't take that left! Just keep going straight  for another few minutes where the Mormon Trail dead-ends into the National Trail. Once you get to this point, you have the options to complete the loop either clockwise or counter-clockwise. (Some suggest that going counter-clockwise is easier to navigate to Hidden Valley Trail.) 

Going counter-clockwise, one of the first thing's you will encounter is Fatman's Pass; which is a rock formation that is a narrow crack in a boulder approximately 8 feet high and 15 feet long that you will have to "squeeze through". Fatman's Pass tends to go over well with younger hikers as it gives them a fun area to explore. 

After you go through Fatman's Pass, you'll be led to Hidden Valley Trail. 

The Valley is about 0.5 mile long and there are numerous trails going through it. You can't really get lost, so just continue down the valley and feel free to follow whichever path suits your fancy. There are lots of little caves/nooks and tunnels to explore in the valley so feel free to take your time exploring. The exit from Hidden Valley is as spectacular as the Fatman's Pass entrance. It consists of a 40 foot natural tunnel through the rock formations, and is also a fun place to spend time exploring.

After exiting the tunnel, continue 50 yards or so to the signed connection to the National Trail. Turn left (West) and follow the National Trail for 0.1 mile to the junction with the Mormon Trail, which you then follow back down to the trailhead. If you didn't enjoy the views while you were huffing and puffing up hill, make sure you enjoy them on the more leisurely descent! Courtesy of hikearizona.com