Slovenia was a surprise hit for me. I drove around Slovenia on a whim, having known very little about Slovenia. Ljubljana turned out to be one of my favorite European capitals - such a beautiful city to walk around. Lake Bled everyone knows, and it quite nice in person. Vintgar gorge, the caves, the castles, the plentiful (and delicious) wine.
Outside of Lake Bled, Slovenia seems to fly under the radar as a tourist destination, but it's one of my favorite places in Europe