
The Primtalsperre near Nonnweiler in the Saarland, almost France, can retain 19,85 Mio. m³ water.
Since Keanu Reeves was cloying my brain after I read the prompt I looked up the word “matrix” in the dictionary. Turns out it comes from Latin (surprise!) and it means either “uterus” or “dam” (as in a mother in the animal world). So: mama spidermonkey to the rescue. Very protective of her baby, including the safety tail wrapped around the rope.

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