Hidden Valley (Fat Man's Pass)
Mormon Trail to Hidden Valley loop · Mormon Trailhead
Photo: ksblack99 · Public domain- Distance
- 3.7 mimi
- Climb
- 921 ftft
- Est. time
- about 1 hours 40 minutes
- Difficulty
- Moderate
A loop from the Mormon Trailhead up to a boulder-filled valley on South Mountain with a natural tunnel, a smooth rock slide and the narrow squeeze of Fat Man's Pass.
This loop climbs the Mormon Trail up the north side of South Mountain, follows the National Trail along the ridge, and drops into Hidden Valley, a pocket of boulders tucked into the mountain. The best parts are close together: a natural tunnel, a smooth rock slide, and Fat Man's Pass, a narrow squeeze between boulders. The boulders give some shade; the climb up doesn't. The City notes petroglyphs along the Mormon Trail.
- Parking
A paved lot of about 30 spaces in a residential neighborhood, with street parking nearby; watch for no-parking signs.
Trailhead: Mormon Trailhead.
- Fee
Free
- Dogs
- Dogs on leash
- Shade
- Minimal
- Hazards
- The City of Phoenix closes this trail 8a–5p on Extreme Heat Warning days.
- No dogs on City trails when it’s above 100°F.
- The Mormon Trail is steep in places.
- Fat Man's Pass is a tight squeeze between boulders, with a smooth rock slide to get down.
- Best months
October to April, when the average high in Phoenix is under 90°F.
- Sources
8 sources · last verified Sep 24, 2026. Report a change
Photo: ksblack99 · Public domain
Where each fact comes from
- South Mountain Park/Preserve trail map — City of Phoenix (PDF) checked 2026-09-27
- South Mountain Park/Preserve — City of Phoenix Parks and Recreation checked 2026-09-24
- South Mountain Trails — City of Phoenix Parks and Recreation checked 2026-09-24
- Hiking and Trails (leash and heat rules) — City of Phoenix checked 2026-09-24
- Free: the City lists hours and rules for South Mountain but no fee checked 2026-09-24
- Hidden Valley via Mormon Trail — Simply Wander (undated) checked 2026-09-24
- Hidden Valley via Mormon Hiking Trail — AZutopia (undated) checked 2026-09-24
- Best months: normal high under 90°F, Phoenix Sky Harbor 1991–2020 (NOAA NCEI) checked 2026-09-24
Low heat risk · now
73°F now · high 85°
Sunset 5:49p · ~1h 40m hike
As of Today 9:42a · NWS forecast · NWS alerts · NWS HeatRisk
Next 6 days · high / low · NWS HeatRisk today 1 of 4
- Tomorrow88° / 69°
- Wed83° / 73°Rain 76% 6:12a–5:47p
- Thu77° / 67°Rain 62% 6:13a–5p
- Fri73° / 62°
- Sat75° / 59°
- Sun79° / 59°
From the trail
Field notes
Owen · Mormon Trail to Hidden Valley loop · May 2025
I've done this hike multiple times, and each time it delivers. It's a fun hike with opportunities to scramble up some boulders and of course squeeze through "Fat Man's Pass" (there is a way around it if you don't like tight spaces). I haven't had a problem with it being crowded, but expect more traffic on weekends. The most recent time I went there was a rattlesnake laying up close to the Natural Tunnel. The climb up also has good views of the city.
Nearby
Phoenix
