The humble and picturesque NSW coastal town of Kiama is home to one of the state's most impressive national phenomena - the world's largest marine blowhole that sees amazing volumes of water sprayed up to 25 metres into the air under ideally rough sea conditions. The area adjacent to the blowhole is equipped with a purpose-built viewing platform allowing for the best possible shot of the jets of water at work, and its regular and rhythmic nature means you'll be able to see multiple displays in action in short order.
There's also a not-insignificant noise generated by the blowhole - plus, it's one of the few natural attractions on this list where you'll actually WANT to visit on a windy or slightly unpleasant day to see it at its best. Sometimes, the simplicity of nature makes for the most impressive attractions, and this is definitely the case here.