Ljubljana Castle reopened 4 May, and another of Slovenia’s most visited sites, Bled Castle, will be welcoming visitors again from 14 May on. However, note that you’ll not be able to visit the island until 18 May.
In other news, Postojna Cave, by some counts the most popular tourist attraction in the country – since Ljubljana Castle gets multiple visits from locals each year – will not be opening until at least 1 June, although this date remains to be confirmed.