Croatia
On 12 March the Croatian government announced that it will introduce with immediate effect a compulsory 14 day period of self-isolation for all foreign nationals arriving from the following destinations: the United Kingdom, France, Germany, Switzerland, Spain, Austria, Netherlands, China, the Republic of Korea, Japan, and Singapore. Foreign nationals who do not have a residence in Croatia will be asked for proof of an accommodation booking.
https://www.gov.uk/foreign-travel-advice/croatia
(Copied from the Wiki - I think it might have been posted by Stewie Mac?)