Though there are traditional hotels in Ljubljana like the Hotel Union, I chose and recommend a more contemporary spot.
Vander Urbani Resort: Four older townhouses were combined to create this 16 room boutique hotel. It has a very sleek, contemporary design and is a member of Design Hotels which I follow and enjoy their properties. I enjoyed my room overlooking the river. They have a small rooftop bar and pool area with great views of the Castle. There is a bar, Bubbles Bar & Wine Cellar, and their Vander Restaurant serves the breakfast buffet as well as lunch and dinner. Their chef is Benjamin Launay from France.
Having just arrived I enjoyed dinner in the restaurant with a stuffed salmon dumpling and a nice glass of Slovenian red wine, a Movia cabernet. I had no idea that Slovenia produced wine. They are just off the pedestrian mall. One piece of advice, contact the hotel if you are arriving in the afternoon or evening at +3861 200 90 00, for help with your bags. They are just off the pedestrian mall in the center of the old town and taxis are not allowed into that area after 10am. The location is really good for walking and exploring the sites and museums. Krojaska Ulica 6-8.