Wli waterfalls are the largest in Ghana, and are beautiful and well worth seeing. You can get to the lower falls easily through a half-hour track through the forest (flat), and they are lovely, and you can swim in at the bottom. However, the area around is none too clean. In comparison, the upper falls are in a more pristine condition and the swimming area was much nicer. Because the upper falls are not as large as the lower falls, you can (if you're brave!) sit on the rocks by the falls or go underneath it, which is really exhilarating! To get to the upper falls, you must hike - I would recommend doing the longer 'loop' hike, as you climb through mountains and grasslands as well as woodland, though be prepared for a couple of hours climbing followed by an hour or so descent that sometimes borders on dangerous. Ensure you bring at least 3-4 litres of water and sun screen (you'll sweat buckets). The hike is tough, but not too bad if you have a reasonable level of fitness. You need a guide to hike, and sometimes they can charge a lot - try and negotiate. We paid 15 GHC each, which was possibly too much. Would definitely recommend the whole experience though!