The Steall waterfall is some 120m high. It is said to be the second highest waterfall in Britain. Access to the falls is by a path through the Nevis Gorge. Normally the river through the gorge is fairly benign - I believe you can canyon through it - but the weekend we were there the river levels were spectacularly high and you would have drowned very easily, without a doubt.
The falls can be seen from Steall meadow, as above. To get right underneath them you have to cross a wire rope bridge across the river. It's good fun and fairly easy. I don't have any photos of it but this website has photos of the Steall rope bridge.