I’m not totally sure where this is, but the video description says FEB Hrádek, and other videos by MrSmahy mention www.feb.cz, which is the East Bohemia Freediver club in the Czech Republic. Hrádek means ‘small fort’ in Czech, there is a map here on their site mentioning Hradec close to the center of the map. I love how they park their slippers on the ice :-)
