{The Great {Barrier|Obstacle} {Reef|Coral Reef} {Is {Visible|Noticeable}|Shows Up} from {Space|Area|Room} {Stretching|Extending} over 2,300 kilometers, Australia's Great {Barrier|Obstacle} {Reef|Coral reef} is the {largest|biggest} living {structure|framework} {on {Earth|Planet}|in the world}. Its {vast|large|huge|substantial} {coral|coral reefs|reefs} {colonies|nests|swarms} and {marine|aquatic} biodiversity are so {expansive|extensive|large} that astronauts can see them from {low|reduced} {Ea...