Carrell's Ledge is one of the poorly-kept secrets of Table Mountain. It's an absurdly unlikely traverse across the cliff face at the top of Ascension Buttress, overlooking the Pulpit and Newlands Forest, which is where you would land up if you missed your footing on your way across. There are some breathless accounts on the web about how it's "only 20cm wide" (slightly wider than the white line in the middle of a road), which is a bit of an exaggeration, but nonetheless it is a spectacular crossing.
There's a rather overgrown path, not marked on the recent maps, and the start is fairly hard to find, and this is really not somewhere you'd like to get lost. So please don't try it unless you know what you're doing, and don't even think of trying it in bad weather.