Jezerní štola, Mining adit near Jezeří Castle, Czech Republic.

Jezerní štola is a horizontal mining passage near Jezeří Castle in Northern Bohemia that extends into the mountainside. The tunnel system displays the layout of a typical extraction operation with passages and chambers left by miners in the rock.

Jezerní štola was driven in the Middle Ages with hammers and iron tools to mine iron ore. It was rediscovered between 1973 and 1976 during mapping of the forefield of the ČSA open-pit mine, when a concrete shelter was built at its entrance. The adit is 62 metres long, 60 to 100 centimetres wide and up to two metres high.

The mining passage reflects the local tradition of extraction that shaped generations of workers seeking minerals in these mountains. The site shows today how people worked with their hands and simple tools before modern machinery transformed the industry.

Access is via marked paths leading to a stable entrance area where visitors will notice the cool temperature and moisture of the underground space. Sturdy shoes and a jacket are recommended since it stays cool below ground and the floor can be uneven.

The adit is only 62 metres long, 60–100 cm wide and up to two metres high, dug in the Middle Ages with mallets and iron tools to extract iron ore. At its far end a spring of iron-rich water rises; it was once considered healing, and locals carried it away in stoneware vessels, many of which, and their shards, were found near the entrance.