This small lake outside Stockholm, Sweden, emits otherworldly sounds as Mårten Ajne skates over its precariously thin, black ice. “Wild ice skating” or “Nordic skating” is both an art and a science. A skater seeks out the thinnest, most pristine black ice possible -- both for its special smoothness, and for its high-pitched sounds of cracking. This is so exhilarating to watch!!!!!
View full screen if you are watching this video on a computer. It is truly amazing and don't forget to turn on the sound. If you cannot see the video, here is the link for a National Geographic feature on YouTube.