One of my favorite counties in Europe is Slovenia. I love to be outside and appreciate natural beauty (trees, mountains, waterfalls), so Slovenia was perfect. We drove from Germany to Lake Bled (about 8 hours from Kaiserslautern) and brought Henry (our dog). Lake Bled was the busiest place we visited in Slovenia, but it is still a quiet area in comparison to most other places in Europe.
There is a beautiful walking path all around the lake. To get to the church on the island, you need to take a boat. Bled Castle is perched on top of a ridge and looks as if it could fall into the lake from some angles. You can walk or drive up to the castle and from there get some wonderful panoramic views.
My husband loves to scuba dive and is always looking for off the beaten path places to dive...usually more like Palau than Lake Bled, but he figured when else would he have this opportunity? The diving was ok---no huge fish or anything colorful, but the cold climate of the lake has some species of marine life that are not often found in other dive sites.
After Lake Bled we headed to the Soca River Valley. The GPS said something like 50 miles, so we thought an hour or so. What we didn't realize is the route is literally up and over a mountain pass. It is gorgeous scenery, but the road has about a million switchbacks and at some points is very narrow. We were happy once we reached the other side :) The Soca River valley is known for rafting in the summer and skiing in the winter (not world class skiing, but decent skiing). We traveled here in September and it was already turning chilly (even has some flurries at night...this was all new snow on the mountain).
We stayed just a couple of miles outside of one of the small towns and felt like we owned the place. There were more cows than people. We stayed in a small apartment that was part of a working farm. We ate dinner and breakfast with the owners and there were only a few other guests. It was a perfect place to explore....but if this is too quiet for you, stay in one of the main towns and there are restaurants, shops and bars to entertain you while taking in the natural beauty.
On our way to Croatia, we stopped to see the Lippenzzaner horses. Slovenia was one of the original breeding locations for these horses and the area holds on to the tradition. You can see the horses perform on-site. This isn't my thing (my husband was interested, I went for a hike with Henry), so I don't have any photos, but this is something that can done either as an overnight stay (there is a nearby town) or as a day trip. It is about an hour north of the Croatia border.
We stayed in Opatija, Croatia which is about 40 minutes across the Slovenian border. Opatija is a historic beach town and it has a beautiful wooded walking path along the coast. The beaches are all rocky in this area and there are only a few places suitable for swimming (mostly at established swim/beach clubs).
We drove inland to see Plitvice National Park. We arrived in the middle of the day (around 1:30pm), which in hindsight was a mistake. Even though we weren't there in peak season, it was still very crowded. Think about probably 30 bus loads of people.....all in a pristine beautiful park. The two don't mix very well. We started walking (the park is dog-friendly) and it was like a traffic jam...wall to wall people..so much so we considered leaving. After an hour or so of walking, we noticed most people were turning off the trail at a spot where the main trail continued. We learned from our innkeeper that is where the buses are and most leave around 3pm. Sure enough, after that turn off, we lost about 90% of the people and could finally enjoy ourselves (so early in the morning and after 3pm are the best times to visit).
I highly recommend a visit to Plitvice and it is worth taking your time to explore. There are trams that take you from one part of the park to another and you can either start or end with a boat ride across one of the larger lakes (saving about 2 hours of hiking time). I also recommend staying in the area overnight, so you have flexibility to go when it isn't as busy (it made a huge difference for us).