Kamencové jezero is one of the most extraordinary lakes in the world — a natural body of alum water sitting at 337 metres above sea level on the north-eastern edge of Chomutov, Czech Republic. With a pH of around 3, it is often nicknamed the 'Dead Sea' of Bohemia, yet it still draws thousands of visitors every summer season.

The lake stretches 676 m in length and 240 m in width, reaching a maximum depth of just four metres. Its acidic water, rich in sulphates, iron and dissolved alum, means no fish or higher organisms can survive here — but scientists have identified around thirty species of aquatic microorganisms and insects, making it a genuinely fascinating natural phenomenon. In summer the grassy and sandy beach, a large jetty with pools and a water slide, plus boat and paddleboard rentals make it a lively family destination. Off-season, the mist hanging over the glassy surface and the surrounding greenery create a wonderfully atmospheric, almost eerie scene.

• Chomutov town centre / lakeside car park — easy walk or cycle along local paths, easy

• Swimming area open from 1 May to 1 October
• On site: campsite, restaurants, boat, pedalo and paddleboard hire
• Motor boats are legally prohibited on the lake
• Water pH is approximately 3 — visitors with sensitive skin should take care

The historic alum spa building once treated respiratory ailments, rheumatism and anaemia; today it serves as the administrative centre of Chomutov Zoo — a charming reminder that this unusual lake has been healing and fascinating people for centuries.