Spires Gully is the easiest descent route from the hanging Bridalveil Canyon found above the falls of the same name. Located just south of Higher Cathedral Rock and west of Higher Cathedral Spire, it is often used as a descent route for rock climbs that end at the summit of HCR. The entire route is class 2, most of it easy on a good use trail.
If coming from the west, go east on Southside Drive past Bridalveil Falls and Cathedral Rocks. Park at the turnout on the right side of the road just before the junction with the road coming from El Cap Meadow (this is signed as a left turn for exiting the valley). Head south from the road on a use trail, crossing the maintained Valley Loop Trail, and picking up the use trail (marked by ducks) on the other (south) side of the trail.
If coming from the east end of the valley, turn left at the triangle marking El Cap Meadow, and drive south to the junction with Southside Drive. Park on the left side of the road just before turning onto Southside Drive. The trailhead mentioned above is about 50 yards west on the one-way Southside Drive.
Follow the use trail south of the Valley Loop Trail, past a bouldering area and through the forest. The trail is well-travelled in this lower section as it is used for access to the bouldering area, climbs of Higher Cathedral Rock and the Cathedral Spires, and descents down Cathedral Gully. Take right forks (a left fork heads to Lower Cathedral Spire), angling for the northwest side of Higher Cathedral Spire.
The use trail begins to climb steeply near the base of a boulder-filled gully, and soon is lost amongst the rocks. Numerous ducks can be found from here to the top, most of which do little more than mark the passage of another climber. You don't need to follow the ducks to find the way (in fact that might take longer), simply follow the easiest route up the gully. Do take the time to admire the sheer walls of of both HCS and the East Face of HCR as you boulder hop your way up. The broad gully eventually narrows after what seems an interminable amount of scrambling (it's 1,500ft up the gully, 2,000ft from the valley floor).
Near the top of the gully, stay to the left following the easiest route through some large pines to the low point along the ridge. If you veer right (north) there is section of very loose dirt/rock followed by a short 15-foot class 3 section that will be encountered at the very top - this is not the easiest route, though it seems well-used. But it's certainly easier than climbing the Gunsight between Middle and Lower Cathedral Rocks.
From the notch at the top it is a class 2 scramble down to Bridalveil Creek, up to the summit of Higher Cathedral Rock (the highpoint of these rock formations) or south to the valley rim.
None needed. This is the easiest route to Higher Cathedral Rock and probably to Middle Cathedral Rock as well.