August 18 (SeeNews) - Croatian hotel operator Maistra [ZSE:MAIS-R-A], a unit of diversified conglomerate Adris Grupa [ZSE:ADRS-R-A], said on Thursday it has opened a new 300 million kuna ($45.4 million/40.1 million euro) hotel, Amarin, on the west coast of the Istrian peninsula in Rovinj.