This is a classic route. It follows the prominent ridge on Wiwaxy Peak that faces Lake O'Hara. It is ~300 m long, and can be done in 12-13 roped pitches, with plenty of scrambing in between. The route is rated 5.7, and it goes on solid quartzite. Protection is good, and the views of the surrounding peaks and Lake O'Hara are spectacular. Climb this route!
From the Lake O'Hara campground, cross the road and find a well-travelled trail. Cross Cataract Creek on a wooden footbridge and walk the trail upstream for 200m or so until you spy an avalanche gully leading upslope (there was a small cairn here, and the climber's trail is obvious at this spot. Follow the trail (or your nose) up the hill through the trees (also some flagging at the time of our ascent). Work left at some cliffs until you find a way through them, then follow ledges and ramps back right to the base of the route. A lone tree (the highest one) at the base of a large chimney marks the start of the route.
Pitches 1 & 2
Two pitches (5.4-5.5) up the chimney lead to the first of several large ledges. The rest of the route follows the blocky ridge, basically right on the crest, but passing most major impasses on climber's right. Many variations are possible on the ridge, but the most aesthetic line stays on the crest as much as possible. In the interest of preserving your experience, I do not describe the route pitch by pitch, but routefinding is easy and the climbing and protection are superb. As you climb, take time to look around. The scenery is some of the best I have ever seen.
Descent: Work your way to the obvious col east of the ridge. This is 4th class, and in dry conditions, we were able to downclimb. However, many rap stations suggest that this may not be possible for some parties.
Once at the col (DO NOT DESCEND IT!), contour around the S side of S. Wiwaxy tower on ledges (and a climber's trail). Another gully below will tempt you, but stay high and head for another notch to your left (as you are descending; cairn). From this notch, you can see down the proper descent gully and right into Lake O'Hara. Descend loose scree and sand for several hundred meters and catch the Wiwaxy Gap trail back to Lake O'Hara.
Double ropes are handy on this route (some loose and sharp rock). Many long slings (8-10; leave the draws at home). A light rack, stoppers and hexes work well, cams to #2 camalot.
We found the most popular guidebook (which will remain unnamed) to be filled with much useless (read: incorrect) beta.
However, there is a solution. I don't know the folks that put this CD together (really), but it was invaluable in Canada. Have a look and see for yourself. This CD has a detailed, pitch-by-pitch topo of the Grassi Ridge and many other Canadian Rockies classics.