The title says it all...

[![enter image description here](https://i.stack.imgur.com/N88mR.jpg)](https://i.stack.imgur.com/N88mR.jpg)

I assume it requires very slow freezing sheltered from the wind. Undercooled water, maybe?

* A [Reddit thread](https://www.reddit.com/r/pics/comments/2x05t3/frozen_pond_in_switzerland/) talks about [Delaunay triangulation](https://en.wikipedia.org/wiki/Delaunay_triangulation), but that does not explain how it forms.
* Many sites claim it is in Switzerland without further info.
* A comment in [another Reddit thread](https://www.reddit.com/r/interestingasfuck/comments/2qam4b/frozen_pond/) states *It happens when there is a significant change in gravitational force during the freezing process.  

Also, there was a lot of water vapor hovering just above the surface during a rapid freezing process*, but I doubt that gravitational effect.

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BTW While researching this I found this beautiful page [18 Beautiful Frozen Lakes, Oceans And Ponds That Resemble Fine Art](http://www.earthporm.com/18-beautiful-frozen-lakes-oceans-ponds-resemble-fine-art/) - several of the pictures there would merit a separate question ;-)

It has a similar picture claiming to be from a frozen pond In Southern Oregon, USA\*:

[![enter image description here](https://i.stack.imgur.com/CB9Eu.jpg)](https://i.stack.imgur.com/CB9Eu.jpg)

\* But a Google image search finds claims of Switzerland, again.