High on that list has to be the Large Hadron Collider, which didn't destroy the galaxy when it was switched on earlier this year. (It was shut down soon after because of some magnet issues we don't quite understand.) While scientists work to get it running again, tours to CERN's other labs continue.
Also worth scouting out--at least from a distance--is the Lucens reactor, which suffered a partial meltdown in 1969. The underground plant was quickly sealed off, averting a Chernobyl-style disaster.
There are four nuclear power plants currently operating in Switzerland; they provide nearly forty percent of the country's electricity. Three are single-reactor facilities, while the plant in Beznau boasts two reactors, set on an artificial island in the Aar River.
Don't Miss Our Nuclear Switzerland Travel Map.