Is the Subway a normal hike?

No. It is a permit-only backcountry route, not a trail, and it exists in two versions. Bottom-up is the less technical option but still involves a steep descent, extensive boulder-hopping and route-finding, and repeated stream crossings out and back. Top-down is genuine technical canyoneering requiring rappelling, swimming through cold water, and the skills and equipment to match. Neither is a family day out.

How do I get a Subway permit?

Through the National Park Service, by lottery and other allocation methods, and demand consistently exceeds supply. Systems, dates and allocation methods change, so consult the park directly rather than relying on anything published elsewhere. Plan the trip around securing a permit rather than hoping to add the route once you are already there.

What is the main danger?

Flash flooding, by a wide margin. Water can arrive from a storm you never saw, and there is nowhere to get above it once you are committed. The decision that matters is made on the morning of the hike, against the park's own outlook rather than a general forecast, and the right response to an uncertain one is to go somewhere else that day. Nothing else on this route — the route-finding, the cold water, the distance — comes close to it for consequence.

How hard is the Subway hike?

Harder than almost anyone expects from the photographs, and hard in a way that fitness does not fix. The qualifications that matter are navigation and the judgment to turn around, because neither version has a maintained tread to follow or signage inside the canyon, and both put you hours from help. A useful calibration: if the Narrows walked upstream felt like a full day, this is a considerable step beyond it in every dimension except the permit, which is harder too. Parties get into difficulty here most years, and it is generally because they judged the outing by its mileage rather than by its terrain and its daylight.

The Subway: Zion's Iconic Canyoneering Hike

A permit-only route through the Left Fork of North Creek — two versions, neither of them a hike in the ordinary sense.

The Subway is one of the most photographed places in Zion National Park and one of the least casually accessible. It is a permit-only backcountry route through a section of the Left Fork of North Creek, where water has cut the sandstone into a smooth, tubular passage that genuinely looks engineered.

It is not a hike in the ordinary sense

This is the thing to understand before anything else. The Subway is a route, not a trail — there is no maintained tread, no signage inside the canyon and no one coming to find you — and it exists in two versions that share a name and almost nothing else.

Bottom-up is the less technical option. A long approach involving a steep, loose descent from the rim into the canyon, then extensive boulder-hopping and route-finding upstream with repeated crossings, and the same again in reverse. No ropes are required. It is nonetheless demanding, slow, and hard on ankles and knees, and the climb back out at the end comes when you are least interested in it.

Top-down is genuine technical canyoneering: rappels, swimming through cold water, and the equipment and training to do both safely. It is a one-way traverse requiring a car shuttle. This is not something to attempt on the strength of an article or a video, including this one.

Neither version is a family day out, and people do get into serious difficulty here by underestimating the gap between the photographs and the approach to them.

The permit governs everything

A permit is required for both versions, allocated through the National Park Service by lottery and other methods, and demand consistently exceeds supply.

Systems, dates and allocation methods change, so consult the Park Service directly — nothing published elsewhere should be relied on for the current process. The planning consequence is the durable part: build the trip around the permit rather than expecting to add one.

Flash flooding is the serious risk

A narrow canyon with a stream running through it, in a desert that gets its rain in violent bursts, is a flash-flood hazard by definition. Water arrives from storms falling miles away on ground you cannot see, and in a slot there is nowhere to go.

Read the park's flash-flood outlook the morning you go, not the night before, and turn around on an uncertain forecast. From midsummer into early autumn, when the storms are routine, that judgment is the single most important decision attached to this route.

Cold water, and what it does to a day

Both versions involve being wet, in shade, in water that stays cold year-round because the canyon walls never let the sun reach it. Hypothermia is a more realistic hazard here than heat, which inverts the usual desert calculation. Quick-drying layers rather than cotton, and for the top-down route a wetsuit or dry suit for much of the year.

Do not plan to drink from the creek. Harmful cyanobacteria have been documented in Zion's waterways and no recreational filter removes the toxins they produce.

Be honest with yourself

The Subway rewards fit, experienced parties with navigation skills and a full day of daylight. It punishes people who came for the photograph.

If the description above sounds like more than you want, the park's headline experiences are far more accessible: the Narrows walked upstream from the bottom needs no permit at all and delivers a comparable sense of being inside the rock, and Emerald Pools suits any ability.

Practical

Start very early. This is a full day, and finishing in the dark in a canyon is how difficulties become emergencies.
Proper footwear for wet rock, and expect to be in cold water regardless of season.
Tell someone your plan and your expected return time, and stick to it.
Carry more water and food than the distance implies — route-finding is slow, and the distance is a poor guide to the hours.
The trailhead is on Kolob Terrace Road, well away from the canyon and its services. Fuel up and buy what you need before you turn off.