I feel that a lot of the comments made here abt people being crazy flying through / over / around the mountains in a single engine have never done it before and therefore have no experience in this matter.
You would be wrong
You can easily fly from the north to the south of Switzerland via the passes at around 8000'. I'm often doing this in a single. Just make sure you have got yr map with you and stop relying on the GPS!
What a daft comment!
The context here is IFR, airways, flying (as one should) VMC on top in sunshine, above the clouds etc, out of icing conditions, at a safe altitude. Not scud running through the Swiss/Austrian/Italian canyons, hoping that the cloudbase will not meet up with the rising terrain, and hoping that you did not misread the map and flew into a canyon where you get stuffed - as many do when doing that kind of flying.
One can indeed cross the spine of the Alps at about 8000ft but this is possible only under VFR, not under an IFR clearance. And you better hope there are no clouds around when you do that, or significant wind when flying that close to the terrain.
I've been to the Alps, with a local expert, doing that kind of flying, and it was great fun on the (carefully picked) day. But for going places - no way. The safest way is to fly straight across the top at FL160 or higher, in VMC, and for that you have to be IFR. Zurich will not allow transit through their FL130-base Class C.