Mt Hay Canyon, often known as Butterbox Canyon, is a short but spectacular canyon on the southern edge of the Grose Valley. The main drop is quite awesome, and can be difficult and dangerous in high water, but the main constriction ends soon afterwards. Most parties exit via a short but exposed rock climbing pass that was popularised (and possibly discovered), by Tom Williams in 1977.
The canyon was first descended by a party from the Sydney Technical College Bushwalking Club (now UNSW Outdoors Club) in 1954. Early parties used to exit via the Blue Gum Forest and the Lockley Pylon track, making for a long day. Until the early 1960s it was a particularly long day as the fire trail to Mt Hay was only put in around then.
The entry route has recently changed to avoid crossing a hanging swamp. There is a sign board at the car park with a map showing the new route, described below.
Drive to the end of the Mt Hay Rd at MGA590758 (Katoomba). Follow the main track to the north until it branches after 200m, and take the left branch. Continue for another 250m until you reach signs indicating the track to the canyon on the left. Follow this down the ridge to the south. You should reach the cliff line at a 3m corner, with a log book. The corner can be climbed down. Use a rope if necessary as a handline. Continue down to the creek, and follow it down to the first abseil. There are 4 drops up to 15m in the creek itself. The second (2m) can be combined with the first with a long enough rope, or bypassed via ledges on the right. The fourth can also be avoided by crossing over the small creek and scrambling down the ridge opposite.
Once in the main creek (Rocky Points Creek) make your way downstream. There is a bit of scrambling, and one place where a rope can be used to hand over hand or abseil. There is also a fairly straightforward scramble to avoid this. Immediately after this drop, a 20m swim marks the beginning of the canyon, and the ledge above is a good place to put wetsuits on.
There are a couple of swims, and then the first drop in the canyon is reached. This is about 9m from a tree on the right, or jump into the pool (check depth). Scramble down slippery boulders to the main drop. The main drop can be done in two stages - the first about 20m from ring bolts to a large chockstone, and then another 20m from bolts above the chockstone to the bottom. The first person down should be a good abseiler, as getting on to the chockstone can be difficult. It is useful to have two ropes so that not everyone needs to crowd onto the chockstone. Use a safety line while you are on the chockstone. The second pitch is typically done in front of the chockstone, but can also be done behind, though behind can be tricky in high water.
Then there is an abseil/downclimb of about 4m, followed by a 2m jump, and then the canyon opens out. The next drop down a sloping waterfall looks high, but can be scrambled down on the left via a series of ledges. There is an optional waterjump near the bottom. There are also slings on the right. There is another couple of hundred metres of scrambling and boulder hopping, before a final 12m abseil from the left of the waterfall.
There are several options for exiting.
The most common involves a short but exposed rockclimb to connect two sections of track.
From the bottom of the final abseil, climb directly up to the cliffline on the right, and follow the cliffline around to the left. This descends down into a gully, then very steeply up the gully. There is then a small downhill, followed by a more gradual uphill, passing a couple of ledges, until you can get up to a wide ledge. Follow the ledge back to the right for 300m (becoming exposed), through a cave, to the start of the climb. The climb has 5 fixed hangers and double ring bolt belay at the top of about 8m of climbing, so is very well protected. It is around grade 10, so while not too hard, the holds are dusty and worn, and climbing without proper shoes is tricky. It is also quite exposed.
At the top, head around to the right to climb a steep eroded gully that leads to a saddle. There is a superb lookout to the right, with views back into the canyon. Otherwise head left and follow the track up until you can find your way back to the car.
The non-climbing exit is very rarely done these days. It probably adds around 4 hours to the day. It involves following the creek down to the Grose River, walking upstream on the Grose to the Blue Gum Forest, and then up the Lockley Pylon Track back to the Pinnacles. Then there is a road walk back to the car.