The Egagropili, widely spread throughout much of the Mediterranean basin, are spheres of ruffled algae deriving from the Posidonia oceanica plant, characterized by some advantageous properties for the construction industry: – high CO2 absorption capacity; – long life cycle, durability and resistance; – fire resistance (class B2); – excellent thermal insulation values. The project involves the use of this material fibrous as a covering, thus combining the aesthetic aspect with a marked sensitivity towards environmental sustainability. The adoption of Posidonia oceanica represents, in fact, an ecological and conscious architectural choice, in harmony with the needs of the architecture of the future.