It's hard to put a price on some things.
But Deloitte has still had a go. It's calculated that Australia's Great Barrier Reef is worth A$56bn (£33bn; $42bn).
That's the reef's total "economic, social and icon value" so including attracting touirsts, supporting jobs, plus the "brand value" to Australia of people associating the country with the striking natural ecoystem.
That makes it 12 times more valuable than the Sydney Opera House, according to the Great Barrier Reef Foundation, which commissioned the report.