Some spots not miss include Dragon Bridge (especially with kids), Triple Bridge, the beautiful pink-red exterior of the Franciscan Church of the Annunciation, and the charming streets around the Ljubljana Cathedral.
We visited the castle first early in the morning, had a picnic lunch, then took an early afternoon tour of the cave.
The girls loved the train ride that took us deep into the cave, where we then took a guided walking tour through about 1.5 kilometers of the limestone cave system with all its gorgeous formations.
Definitely plan to have lunch at Koca na Vojah on your hike to Mostnica; the Slovenian barley stew and mushroom soup were delicious there and perfect for a hiking lunch on a fall day