A great excursion from Zürich is the half-day trip north to the Rhine Falls (rhinefalls.com), Europe’s largest waterfalls, 3km west of Schaffhausen. They are magnificent, not so much for their height (just 23m) as for their impressive breadth (150m) and sheer drama, with spray rising in a cloud of rainbows above the forested banks and the turreted castle, Schloss Laufen, on the south bank. Come on the national holiday, August 1, for the famous fireworks display. In summer, the best views are from daredevil boats (maendli.ch), which scurry about in the spray from Schloss Laufen or Schlössli Wörth, across the river, from where a restaurant gives a great view of the falls.
Take a train to Schaffhausen then bus #1 to Neuhausen Zentrum, or a local train to either Laufen am Rheinfall (below the castle; April–Oct) or Neuhausen; you can also walk in 30 minutes from Schaffhausen to the bridge above the falls.