Underground tunnels are situated northeast of St. Wenceslas´ Church. No written records about these underground tunnels and their original purpose have been found so far. The last surveys including rough geodetical location and probably cleaning up the underground tunnels were done during World War II in 1944. Later the underground tunnels were visited only by inquisitive boys from Světlá and – unfortunatelly – used as a dump by local citizens.
A group of members of National History Association of the Region of Světlá with understanding and help of the Municipal office of Světlá started to clear up underground tunnels. Apart from decontamination and safety work in places where threatened danger of injury of unauthorized persons, the lights and an entrance hall with a little exhibition were installed.
After cleaning up all the underground structures in 1999-2002 was found out that the total length of the underground tunnels including blind alleys is almost 200m, all of them ending in hard rock. No connection to other underground spaces has been found, failing to confirm the folk myths about the connection between the underground tunnels and the cellars of local medieval houses or the stories about passages and tunnels erected under the river Sázava heading to the chateau or even to Lipnice castle. Neverthelles the tunnels are an exquisitive example of medieval construction skills although their purpose can be only suggested from similar systems in other towns. The oldest parts of the system are in a rock outcrop above the river Sázava as was proved by character of the works and their proceedings. These were two cellars attached to today non-existing buildings. During the time underground structures expanded and interconnected, transforming into a relatively unified structure with tunnel width ranging from 160 to 240 cm and tunnel height of 170 to 210 cm. Tunnel walls and ceilings make wanderful arches with traces left after the hand tools used to hew them out.
The age of the underground tunnels is not certain. The oldest entrances are situated near expressive tectonic structures and therefore it is probable that first surveys were done by prospectors at the end of 13th century as in neighbouring towns Havlíčkův Brod, Ledeč nad Sázavou, Jihlava and others. Most of the tunnels probably developed step by step and together with the owners the underground structures changed their usage. However,the quality of tunneling work reveals that the most characteristic features of the underground date back to the 15th century AD as can be seen by the quality of the works. Nevertheless, later cuts and adjusting of the surface is also possible.
The oldest findings of chips and pottery are from 15th century. It is probable that underground was a subject to occasional thorough cleaning especially when used as a storage space for food. The only coin found dates to the year 1800.
Todays united underground structures were originally led from two different places owned by different landlords. South entrance was connected to the cellar of the house n. 15. The house used to be jewish or czech-brothers chapelry (today destroyed). South entrance had been built earlier than the house n. 15. The second originally individual entrance was situated in the same rock outcrop 17 m in northern direction against the river flow. This oldest descent of todays structures was ony 5 to 6 m deep and it is a subgrade part of the underground structures today. New building of the tunnels developed as the town was growing bigger. It seems that originally individual cellars were built for needs of individual families and later created a common system.
Approximatelly in the central section of the underground systems workers accidentally drove to an old well with an area of 1 sq.m., depth of 9.8 meters and with a bottom situated 3.25 meters under the floor level. The level is of circular average and was hewn into a paragneiss and exhibited low-volume inflow, therefore serving mainly as auxiliary ventilation. The main ventilation system consisted of perpendicular boreholes with 10 cm diameter and 4 to 6 meters length.
Text: Ing. Jan Dudík