Carnival Corporation has signed a multi-billion dollar contract to build four of the greenest cruise ships in the world – and they’ll also have the largest guest capacity at sea!

The vessels – to be released between 2019 and 2022 – will be the first cruise ships to be powered by Liquefied Natural Gas (LNG), the world’s cleanest burning fossil fuel. Using LNG to power the ships in port and at sea eliminates emissions of soot particles and sulfur oxides.

In addition, each ship will be able to carry 6600 guests and feature more than 5000 lower berths.

Carnival Corporation CEO Arnold Donald said the vessels will also aim to make better use of public spaces.

“These are exceptionally efficient ships with incredible cabins and public spaces,” says Donald. “Every step of the way, our focus is on designing state-of-the-art ships that provide a vacation experience our guests will love, and we are putting all of our creative energy and resources into making sure we achieve that goal.”

Two of the ships will sail under the AIDA Cruises brand, while the other two will be part of the Costa Cruises group.