The lights are even nicer at night! They just add to the look of Ljubljana and turn the whole city into a fairytale town. There's some simple lights in the trees of Castle hill and the castle changes colour every minute. Some of the houses get a frame of lights and the trees and streets turn into a sea of lights. Ljubljana really should be on your list of places to visit in christmas time!
On the picture you can see the tourist information building by the way so this is a double Local Customs tip ;)
Unlike the christmas decorations in many other cities the ones in Ljubljana look great during the day as well as at night. Apparently every year another local artist designs them so they change. Very creative and very nice I think.