I will give you some ideas on what to see in Slovenia if you can only spend three days.
Day 1
For most people who don’t live in the neighboring countries, your first contact with Slovenia will probably be the Ljubljana airport (officially called Letalisce Jozeta Pucnika). If you decided to travel on your own (not with an agency) and want to see as much as possible in three days, it is best to rent a car at the airport.
First I suggest driving to Bohinj. It takes about 1 hour by car if the roads are not too crowded. Bohinj’s main attraction is the largest permanent lake in Slovenia. It is in the Triglav National Park. There are many things you can do. An unmissable attraction is the Savica Waterfall. It takes about 15 minutes of a fairly easy uphill walk from the parking spot to get there. After that I suggest you take a cable car ride to Vogel. It is a very scenic drive with a great view of Lake Bohinj and the surrounding mountains. When you arrive at the top station of the Vogel cable car, you can walk through the surrounding mountains. If you don’t like hiking, you can eat or drink in some of the mountain huts and enjoy the great view of the Julian Alps. When you get down you can go to the beach around the lake. In the summer months the water is perfect for swimming. It is also possible to rent a boat or a kayak. I suggest you also take a look at Mostnica Gorge, located near the village of Stara Fuzina. It is a very interesting place.
The next place worth seeing is Bled, a town you passed through on the way to Bohinj. There are a large number of hotels and other accommodation options. The main attraction of Bled is the lake with an island and its church. Around the lake there is a 6 km long path where you can take a romantic walk in the evening if you still have enough energy after a tiring day.
Day 2
I suggest starting the day by visiting the island in Lake Bled. It is the only island in Slovenia. It can be reached by a boat called Pletna. On the island there is a church where you can ring the bell. When you return, you can continue your journey to Bled Castle, which is located on the rocky cliff above the lake. You can visit the museum and enjoy the beautiful view of the lake. Not far from Bled is the magnificent Vintgar Gorge. If you visited Mostnica in Bohinj, you only saw the gorge from the top. But you can walk inside the gorge where it will appear even more attractive. At the end of the gorge is the Sum waterfall.
The next place I suggest to visit is Ljubljana, that’s the Slovenian capital. It is about a 45 minute drive from Bled. In Ljubljana there are many ways to pass the time. I suggest walking through the old town and taking a ride on the funicular up to the Ljubljana castle. You can go up to the castle tower from where you can see the whole city and beyond. If you like nature you can take a walk in Tivoli Park which is close to the city center. If you like shopping you can visit BTC City where there are hundreds of stores. There are also cinemas (3D), Atlantis Water Park (with many swimming pools, water attractions, saunas…), The Millennium Sport Center and much more. When you’re done shopping or other activities, it’s nice to relax in the old town, near the Ljubljanica river, where there are many bars. I suggest you spend the night somewhere there.
Day 3
On the last day you can go to the beach. It takes about 1 hour to get there on the highway. Along the way you can stop to see the world famous Postojna Cave or the Skocjan Caves. It’s hard to say which one is better to watch. In Postojna Cave there is an interesting train ride. However, I prefer the Skocjan caves a little more because there are more impressive views. After seeing the caves, you can continue driving to see the ancient Mediterranean city of Piran. Take a stroll through the many narrow streets and climb to the top of the church bell tower or the city walls above the city. When you get tired you can sit down, look at the sea and eat some seafood. When you have enough, you can drive slowly back to the airport and catch the plane.
Above are some ideas how to spend three days in Slovenia, of course, this is only one possibility because in Slovenia there are many other attractive places to visit, such as the crystal clear Soca river, the Julian Alps with its picturesque valleys, waterfalls…, old towns (Skofja Loka, Kranj, Maribor…), spas, hills, plateaus for hiking, skiing and much more. The choice is yours.