Rainy days are nothing to fear. It certainly doesn't mean you should stay indoors and hide. This probably goes for any city and is definitely true of Ljubljana.
On one very rainy day we took our kids to explore the beautiful castle perched on top of the hill in the center of Ljubljana. Even though the castle was never home to kings and queens and was used in more sinister ways - as a jail and a fortress, we made stories about what it was like back then.
We came up with dragons and knight fighting in the courtyard, we tried to protect the castle from the siege standing bravely on the walls. We pretended we were prisoners wanting to escape the jail and we counted the many coat of arms painted on the ceiling of the chapel and pick the best ones.
After a few hours of walking around, we realized we had a great time, no bad weather managed to interrupt our play and despite our imagination running wild, we still learned something new.