Clear Frozen Lake in Slovakia's High Tatras: Walking on Transparent Ice

Two friends step out onto a frozen mountain lake in Slovakia's High Tatras, and the ice is so clear that every stone on the bottom shows through. On camera it looks as though they are walking on water, or on air. The video, uploaded on 8 December 2014 by Tomas N with the description "Me and my friend walking on frozen mountain lake in High Tatras Mountains in Slovakia", went around the world within days.

Walking on a clear frozen lake in the High Tatras

In the footage the two hikers walk across the surface while the stones of the lake bed stay in plain view beneath them. Many viewers assumed it was a trick. Snopes looked at the clip in December 2014 and answered the main objections: AccuWeather noted that clear ice is roughly twice as strong as white ice, and that subfreezing temperatures had gripped the region since mid-November, plenty of time for a solid layer to form.

Why lake ice turns crystal clear

Most lake ice looks white or grey. That cloudiness comes from snow falling on the surface and from air bubbles trapped when ice thaws and refreezes. Clear ice, often called black ice because the dark water shows through it, forms in a particular set of conditions:

• the temperature drops quickly from mild to very cold
• there is no snow to settle on the new ice

When that happens on a small, clear mountain tarn, the ice becomes almost like glass, and the lake bed shows through as if there were nothing in between.

The High Tatras and their mountain lakes

The High Tatras are the highest part of the Carpathians, on the border between Slovakia and Poland. Their highest summit, Gerlachovský štít, rises to 2,655 m, and the range was carved by glaciers into steep granite peaks and dozens of lakes, which the Slovaks call plesá.

• Veľké Hincovo pleso is one of the largest and deepest lakes on the Slovak side, 54 m deep.
• Wielki Staw Polski, on the Polish side, is the deepest of the Tatra lakes at 79 m.
• Štrbské pleso gives its name to the best-known resort in the Slovak Tatras, along with Starý Smokovec and Tatranská Lomnica.

Slovakia's Tatra National Park was founded in 1948 and Poland's in 1954. Together they form Europe's first cross-border national park.

Visiting the Tatras in winter

The gateway town is Poprad, which has rail links and an airport, and electric trains climb from there to the resorts. In winter Štrbské pleso and Tatranská Lomnica turn into ski centres, and frozen Štrbské pleso is one of the classic winter views of Slovakia.

Before stepping onto any lake ice, check the thickness yourself. Minnesota's Department of Natural Resources recommends at least 4 inches (10 cm) of new, clear ice for walking, and 5 to 7 inches for a snowmobile. Carry ice picks and a rope, go with a friend, and tell someone where you are going. In the Tatras, also check the national park's seasonal rules: many high-mountain trails close in winter.

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