Located approximately 50km north of Zurich in the town of Neuhausen am Rheinfall, the Rheinfall is the largest waterfall in Europe. It measures 150m in width and 23m in height. Though it is indeed the largest waterfall in Europe (by volume), the Rheinfall is actually rather small. It doesn't compare to a place like Niagara Falls, but it is nonetheless one of the most popular tourist attractions in the Zurich area.
There are a couple ways to enjoy the waterfall. A ferry takes guests right up to the edge of the falls, where you can chill in the mist. An observation deck overlooks the falls and offers great views of Neuhausen am Rheinfall. Schloss Laufen is an old castle that overlooks the falls. The visitor's center here offers insight into the history of the Rheinfall, and also tours. In addition, the castle is home to three different restaurants.
Neuhausen am Rheinfall is along the A4, the first large community past Winterthur. It's accessible via bus and train. The S33 commuter rail line passes through Neuhausen am Rheinfall, with another stop right next door to Schloss Laufen. It will take about an hour to walk from the main train station to the falls, but the town is lovely. The Rheinfall may not be the most impressive of nature's marvels, but is still worthy of an afternoon.
Location: Schloss Laufen