Observatory Rock is composed of typical, and excellent, SSV granite. The crag faces South and South East providing cool climbing in the afternoon. It presently hosts fewer than a dozen described routes, and some combination of guides is probably useful for orientation. I have found the Falcon Guide by Peter Hubble to contain more route descriptions than other sources, however, much of this is misleading. For example, routes listed as 130 ft long have turned out to be more like 65 ft long (truly). Routes span the gamut in terms of difficulty with 5.7 and 5.8 trad or 5.12d sport, although there are not many at any grade. The crag is well worth a day's visit.
5.1 miles up the South Saint Vrain canyon, via highway 7, is a large pull-out on the right side of the road. This can be used for parking for Observatory Rock and the Narrows. Observatory Rock is directly above the parking and has a 5 minute approach.
Mountain Project's determination of some of the classic, most popular, highest rated routes for Observatory Rock:
A good line that will clean up a little more with traffic.Climb up the bottom part on trad gear, which may be the crux for face climbers... continue up to a slab, where you step right, clip a bolt for protection, then step back left under the bolt again, and climb up on a powerful section of flake-pinching and small feet. Finish by trying to pull onto the summit slab gracefully, if you can....[more]Browse More Classics in CO
There is a bolted line to the right of Original route. Perhaps 5 painted bolts with a tree at top behind a bolder for the anchor. Anyone known anything about this route? From the ground it looked like a 5.6 scramble. On the route it felt like a 5.11 frictionfest.
AC wants to know about the bolt line right of Orignal Route: it's called "Will Chevy Slab?", and we rated it 5.10d. 6 bolts, though you need small stoppers to get to the first bolt, and TCUs between bolts 1 and 2. Ends at tree of Original Route (75' rap). The name is a silly word play working off of Wilford Roof, the lefthand of three roof cracks through the big roof on the right (the other two roof cracks are also routes now, though the middle one has not been redpointed to my knowledge - it's quite difficult). Lots of new routes on that crag in the last couple years, mostly cracks with an odd bolt or two, and most of them high quality (the rock there is great). Still working on that SSV guide -- keeps getting bigger all the time, so it'll be a while before it's done.