Not quite 15m, but tall rope pyramids exist in the US. Here's the first one I laid eyes on, in Ashland Oregon on a road trip a couple years ago:

https://photos.app.goo.gl/e15h4rK2NPQvUzH37

Of course I had to climb it immediately. My son was only 2 at the time so he didn't make it far. He's old enough now that I really want to find another one.

I found a few similar items in other parts of Oregon, but I haven't found one in California yet.