@Florencia. If you only have a few days to explore I would recommend picking a few cities that are connected by train, rather than plane. Flying around Europe can be cheap but you'll spend a lot of time travelling to airports, queuing, etc. which will eat into your exploring time. Trains in Europe are reliable and fairly affordable and will drop you in the centre of cities. If your final destination is Switzerland I would recommend flying to Frankfurt and getting the train through southern Germany, ending in Zurich. Nuremberg and Munich in particular are great cities to spend a couple of days in, and the journey through Bavaria to Switzerland is beautiful.