Ciężki Staw (meaning 'Heavy Tarn') is one of the High Tatras' best-kept secrets — a wild, unspoiled mountain lake tucked away in the lower reaches of Ciężka Valley at 1,612 m above sea level. Off the beaten track and accessible only with a guide, it rewards those who seek it with extraordinary tranquility and raw alpine scenery.

The tarn sits beneath the south-eastern wall of Młynarzowe Widły in the Slovak part of the High Tatras. It covers nearly 2 hectares (222 × 125 m) and reaches a depth of around 6 metres. Its waters are fed by a stream descending from the higher Zmarzły Staw, part of which flows underground before reaching the lake — a curious natural feature. The outflowing Ciężki Stream drops over a dramatic 300-metre rocky threshold just below the tarn, forming the impressive Ciężka Siklawa waterfall. In winter, this same cascade freezes into a spectacular ice fall, drawing alpinists to the area.

• There is no marked tourist trail leading to the tarn. It can only be visited with a licensed mountain guide, as part of an ascent to Waga peak from Ciężka Valley.

• Access is permitted only with a licensed Tatra guide — independent access without a guide is not allowed.
• The tarn lies within the protected TANAP national park zone on the Slovak side of the Tatras.

A curious piece of history: for nearly 150 years the tarn was mistakenly called 'Czech Tarn' in Polish, Slovak and Hungarian maps — a translation error that was only officially corrected in Slovakia as recently as 2006.