Císařský pramen, Natural spring in Skalná, Czech Republic

Císařský pramen is a mineral spring in the Soos National Nature Reserve near Vonšov, Skalná. Its water rises in a shallow basin and is captured in a well about 10 metres deep, fitted with a perforated pipe. The spring vase with an outflow into a small tub stands on the site of the original well, and the tub's edges are set with ceramics; carbon dioxide bubbles visibly from the bottom.

The spring was used at the local saltworks before 1843, where Glauber's salt and green vitriol were extracted from its water. In 1876 a vice-regal decree declared it a public healing spring, and in 1877 the name Císařský pramen was approved for selling the water. It was first drilled in 1874 and captured in a 4-metre-deep well in 1908.

The name Kaiserquelle was authorised in 1877 for selling the water, and the spring had been declared a public healing source by decree in 1876. Visitors today see the spring vase set over the original well, with ceramic lining the edges of the small basin, where carbon dioxide bubbles visibly from the bottom.

The location is reachable via well-marked pathways and has resting areas for visitors. Information panels at the site explain details about the spring and its water.

The spring is the warmest natural outflow in the Cheb Basin, reaching up to 18 °C during the year. Its water holds about 2,800 mg of carbon dioxide per litre, so the small basin bubbles visibly from the bottom.