Stříbrné jezero, Opava's Silver Lake

Stříbrné jezero ("Silver Lake") sits on the eastern edge of Opava, in the Czech Republic, in the district of Kateřinky on the left bank of the Opava River. Locals rarely use its official name, calling it instead "Sádrák" – a nickname taken from "sádra," the Czech word for gypsum.

Why gypsum, and why does it matter?

The story of the lake begins with mining, not water. Gypsum extraction in the Opava area dates back to 1849, when deep mining first began on the river's right bank, roughly where the town's municipal gardens stand today. Operations later moved across the river to the left bank, into the area of what was then the separate village of Kateřinky. This deposit held particular significance: it was the only known gypsum deposit anywhere in the Czech lands. The ground gypsum extracted here found two main uses – as an additive in mortar and as an agricultural fertilizer.

How did a quarry become a lake?

Mining came to an abrupt end in 1964. A strong current from the Opava River broke into the quarry and, within the space of a single month, flooded it completely. This wasn't entirely without warning – between 1961 and 1963, water from the river had already seeped into the mining area on three separate occasions, a sign of the instability that would eventually end the operation for good. What had been an active industrial site turned into open water almost overnight, laying the groundwork for what the lake is today.

What is the lake used for now?

Decades after the flooding, Stříbrné jezero has settled firmly into a recreational role. It draws swimmers during the summer season, anglers throughout the year, and walkers who come simply to circle the water on foot. Its location close to central Opava makes it an easy add-on for anyone exploring the city, whether that means a short stop for a walk or a longer afternoon spent by the water. The surroundings have kept a largely natural, low-key character, which suits visitors looking for a quiet break rather than a crowded city attraction.

Is it worth visiting?

Stříbrné jezero works on two levels at once. On one hand, it is a piece of regional industrial history – the site of the only gypsum mining ever carried out in the Czech lands. On the other, it functions today as a straightforward, well-used recreational lake. That combination gives visitors more than just a place to swim: it's a chance to see how an industrial scar can, given enough time and enough water, turn into a landscape feature that a whole city relies on for its outdoor time. Keep in mind that the atmosphere shifts with the seasons – lively and busy in summer, calmer and better suited to a quiet walk the rest of the year.

Frequently asked questions

Why is the lake nicknamed "Sádrák"? The nickname comes from "sádra," the Czech word for gypsum, referencing the material mined at the site from 1849 until the quarry flooded.

When did the lake form? It formed in 1964, when water from the Opava River broke into the disused gypsum quarry and flooded it within a month.

Where exactly is Stříbrné jezero located? It lies in the Kateřinky district on the left bank of the Opava River, on the eastern edge of the city of Opava.

What can visitors do at the lake today? The lake is used mainly for summer swimming, fishing, and walking around its shoreline, making it a popular local recreation spot.

Was gypsum the only thing mined here? Yes – this was the only documented gypsum deposit in the Czech lands, giving the site unusual economic importance until mining ended with the 1964 flood.