Crystal Cruises unveils the world's first self-contained, free-standing 'living wall' at sea, with indoor plants depicting a world map. A living wall is a vertical garden that is pre-planted in panels and then attached to the wall or facade of a building. Plants stay intact in their vertical positions because their root structures are anchored in two to four inches of soil kept within the panel. According to Crystal Cruises a living wall acts as a bio filter, enhancing air quality by breaking down harmful airborne contaminants and transforming them into clean oxygen.