SUPERREEFA

Reproduced entirely from the BLDGBLOG cos of its wonderfulnessness:
The reef's history, from New Scientist: "About 200 million years ago the sea level rose throughout the world. A huge ocean known as the Tethys Seaway expanded to reach almost around the globe at the Equator. Its warm, shallow waters enhanced the deposition of widespread lime muds and sands which made a stable foundation for the sponges and other inhabitants of the reef. The sponge reef began to grow in the Late Jurassic period, between 170 and 150 million years ago, and its several phases were dominated by siliceous sponges."
Rigid with glass "created by using silica dissolved in the water," this proto-reef "continued to expand across the seafloor for between 5 and 10 million years until it occupied most of the wide sea shelf that extended over central Europe."

Thus, today, in the foundations of European geography, you see the remains of a huge, living creature that, according to H.P. Lovecraft, is not yet dead.
What –
"We do not know," New Scientist says, "whether the demise of this fossil sponge reef was caused by an environmental change to shallower waters, or from the competition for growing space with corals. What we do know is that such a structure never appeared again in the history of the Earth." (You can read more here).
For whatever reasons, meanwhile, this story reminds me of a concert by Akio Suzuki that I attended back in London in 2002, at the School of Oriental and African Studies. That night, Suzuki – a Japanese musician and sound artist – played a variety of instruments, including the amazing "Analapos," which he'd constructed himself, and a number of small stone flutes, or iwabue.
The amazing thing about those flutes was that they were literally just rocks, hollowed out by natural erosion – and Suzuki had simply picked them up from the Japanese beach years before. If I remember right, one of them was even from Denmark.
In any case, Suzuki chose the stones because of their natural acoustic properties, their musical playability: he could attain the right resonance, hit the right notes, and so their music was really a factor of geology and landscape design. The accidents of natural erosion.
Rocks everywhere, hiding instruments.

But the idea that there might be a similar such stone flute – only the size and shape of a vast fossilized reef, stretching from Portugal to southern Russia – would suddenly seem like a real possibility. In other words, locked into the rocks of Europe is the largest musical instrument ever made: awaiting a million more years of wind and rain and even war to carve that reef into a flute, a buried saxophone, made of fossilized glass, pocketed with caves and indentations, reflecting the black light of uncountable eclipses until the earth gives out.
Weird European land animals, evolving fifty eons from now, will notice it first: a strange whistling on the edge of the wind whenever storms blow up from Africa. Mediterranean rains wash more dust and soil to the sea, exposing more reef, and the sounds get louder. The reef looms larger. Its structure like vertebrae, or hollow backbones, frames valleys, rims horizons, carries any and all sounds above silence through the reef's reverberating latticework of small wormholes and caves.

Equivalent to a hundred thousand flutes, embedded into bedrock, per square-mile.
Soon the reef generates its own weather, forming storms where there had only been breezes before; it echoes with the sound of itself from one end to the next. It wakes up animals, howling.
For the last two or three breeding groups of humans still around, there's an odd familiarity to some of the reef-flute's sounds, as if every two years a certain storm comes through, playing the reef to the tune of... something they can't quite remember.

It's rumored amidst these dying, malnourished tribes that if you whisper a secret into the reef it will echo there forever; that a man can be hundreds of miles away when the secret comes through, passing ridge to ridge on Saharan gales.
And then there's just the reef, half-buried by desert, whispering to itself on windless days – till it erodes into a fine black dust, lost beneath dunes, and its million years of musicalized weather go silent forever.