That's because the ship's sun deck is designed to replicate a sunny day in the Caribbean no matter what the season. The deck features a sliding glass roof (which can open during summer), fake palm trees and -- here's the kicker -- an "artificial" sun.
Beyond that, Birka Paradise, which will sail 20-hour roundtrips from Stockholm to Finland's Mariehamn, offers the usual cruise ship features, such as multiple restaurants and entertainment options.
Believe it or not, Birka Paradise is not the first ship to sail year-round on Baltic routes. Northern Europe's quite thriving passenger-ferry cruise ships regularly travel between cities such as Helsinki, Copenhagen, Stockholm and Tallinn. However, none have ever tried to replicate a winter's day in the Caribbean.
Birka Paradise, still under construction at Finnyards Shipyard in Rauma, Finland, will launch in November.