Kamencove Jezero

The Kamencove jezero at Chomutov formed in the pit of an alum mine that was worked into the seventeenth century and then flooded, and the water that filled it dissolved the remaining alum shale, giving a solution of aluminium and potassium sulphates with a strongly acidic reaction. The result is a lake described as the only one of its kind in the world: no fish live in it, no aquatic plants grow, no algae bloom, and the water stays clear because nothing can survive to cloud it. It is about sixteen hectares and shallow, and it has been used as a public bathing lake since the nineteenth century - the mineral content is credited locally with helping skin conditions, and the absence of biology means it never needs treating. There is a lido with beaches, a pier, boats and a campsite. It is not a wild place; it is a municipal swimming lake with unusual chemistry.

What you actually see

• Water nothing lives in - too acidic for fish, plants or algae.
• A flooded alum pit - the mine worked until the seventeenth century.
• Permanent clarity - the water never clouds because nothing grows in it.
• A public lido - beaches, pier and boats, used since the nineteenth century.

When to go

June to August. Half a day.

Honest expectations

It is a municipal bathing lake with a ticket and a lido, not a natural setting. The water is chemically unusual and stings eyes. Very busy in hot weather. Chomutov around it is an industrial town.

Nearby

Chomutov zoopark is nearby; the Ore Mountains rise north.