Without many large-scale attractions, it's a great place to simply wander around and admire the architecture. There are plenty of squares, fountains and bridges, including the Dragon Bridge and Preseren Square, the city's central square. The Ljubljanica River runs throughout and there are many restaurants where you can try traditional dishes like potica by the water.
The University of Ljubljana Botanical Garden boasts a Slovenian bee house, alongside beautiful plants and scenery. Beekeeping is so important to the culture that it's on the Slovenian register of intangible cultural heritage in multiple forms and the Carniolan honey bee is a national symbol. If you eat outside, you will probably be surrounded by bees, but they aren't dangerous.
For fans of hiking, it might be wise to take a day trip to Lake Bled at sunrise or Triglav National Park, soak up the crystal-clear waters early and spend the afternoon exploring the city. The winding streets are good for a leisurely stroll, so why not?