Use sunset as your turnaround alarm.
The reason to do this one is that you drive to it. The trailhead sits just east of the Zion-Mount Carmel Tunnel on Highway 9, outside the shuttle system, so you can be walking at first light while the canyon floor is still waiting for a bus. The path is mostly bare rock with stairs and metal handrails on the exposed side, and a few overhangs drop to about four feet of clearance, so watch your head. Parking is the hard part, and there is very little of it.
Massive Zion Canyon payoff for a 30-minute walk. Sunrise gold.
Heat note: desert country - in summer start at dawn and carry more water than feels reasonable.
Water bottle, sunscreen, hat, snacks, comfortable shoes.
Make it a weekend: South Campground (Zion) (Camping, 2 mi) · Watchman Campground (Camping, 3 mi) · Lava Point Campground (Camping, 13 mi) · Kolob Reservoir (Fishing, 17 mi)
More hikes nearby: Watchman Trail (Hike, 3 mi) · Emerald Pools (Hike, 3 mi) · Angels Landing (Hike, 4 mi) · The Narrows (Bottom-Up) (Hike, 5 mi)