.. Ever! If you happen to know anyone who went to Slovenia or at least passing its highway, ask them and they can confirm this.
OK I haven't been to Switzerland or anywhere else that I can compare to, but it's definetely one of the world's most beautiful. Driving on its highways on a clear blue sky or on time of sunrise would make you feel that you're being served by montage of landscapes, from small towns with churches on the hills, farms, vine yards, green hills, forests, to mountains with Julian Alps on the background.
Shall we let the pictures speak for themselves...
When driving East, for example from Ljubljana to Maribor, we always.. I repeat.. ALWAYS make a stop in Trojane for some Trojane Krofi. This huge doughnout-like bread is pure heaven. Yes they do sell krofi anywhere, but they have nothing to compete the original renown Trojane Krofi! I do suggest to have a breakfast in Trojane. It's on top of one of the hill where a tunnel goes through. Just a few hundred meters out from Autobahn.
Of course, the scenery doesn't stop on the highways. If you got out from it and go to its country roads, you'd probably find more beautiful landscapes. I suggest to do a detour to smaller and less travelled roads to explore more of Slovenian landscapes. Wild animals such as foxs, deers, and other forest creatures are not an uncommon sight, so keep your eyes open!