The Chutes de Nachtigal are less a single clean waterfall than a wide, broken rush of water across the Sanaga River. The scale is what makes them worthwhile: slabs of rock, channels of fast water, and local pirogues moving where the river allows.
They sit well outside Yaounde, so this is a day trip rather than a quick city sight. Go with a driver who knows the route, and ask locally about river levels before setting out; the experience changes sharply between dry and rainy seasons.