It is its rich history that ranks the Slavonice town among the most distinguished towns in the Czech Republic. However, it is less known amongst people that a relatively complex and still not entirely mapped out system of medieval underground passages exists under the majority of the houses situated on the Lower and Upper Squares.

Slavonice´s underground passages are one of the oldest parts of the town and they are most likely to be connected with the gothic buildings from the 11th and 12th century. The underground tombs connect to the square. This fact indicates that the original square used to be smaller, mainly surrounded by wooden houses.

First the cellars (vaults) were hollowed out, nowadays so called second floor cellars, which are narrower and passage-like. They have wall niches serving as a storage space for barrels or hand-craft (textile manufacture, food product processing, tannery etc.)

These cellars were later interconnected by passages, in what is called the lowest floor of the underground. This part of the underground has its origin in times when the cellars began to fill up with water, which the town people needed to dispose of.

The passages have different profiles according to whether the passage was a main or last, connecting one. The main relatively spacious passage has a regular profile in the shape of a rectangle. The walls have smoothly finished surface and there is a drainage groove in the floor. Other passages are of an oval, almond or triangle shape ( with convex sides ). The last connecting passages function rather as slips through or punctures into the cellars under the buildings. Some of the inlet branches were enlarged during the sanitation works in order to make it possible to clear the underground. Cotter slots and cuttings left by mining are sparsely preserved on the walls. There are small offsets in one part or other curved into the walls for the placing of burners or of larger aperture for spills ( with the traces of burning out ). The bottom of the passages is somewhere flat with a slope and elsewhere full of gutters. A common feature is a narrow drainage groove excavated into the bottom of the passages. Up to 1 meter deep pits are hollowed out in places, where passages intersect ( and in other places too ), which served for the sedimentation of alluvial sand. There are wells in some cellars, 4 to 5 meters deep, which, with the overall depth of 11 to 12 meters, are as deep as the wells situated on the squares. The average passage profile height is one and a half meter, and it is about half a meter wide.

As well as cellars, the passages are cut manually in often very hard, gneiss rock massif, with the help of a hammer and an iron, without the use of gun powder. The work was probably carried out by mine workers from the Jihlava region. The passages drew off the ground water and water leaking from the near water supply reservoir located on the surface, to the southern moat. The moat used to be approximately 7 meters wide – measured from the top of the rampart walls.

Many indications (such as the arrangement and division of interconnections, and the cleaning overflows and drain pits) suggest that this system had other functions too. It must have been the source of fresh water for the citizens of the town in times of danger, as it was well hidden from the sights or trespassers.

Working shafts for deposition of excavated material have been constructed in the corridors with the distance of 40 – 50 metres between them. After finishing the construction works, these working shafts were roofed over with large stone slabs fit on to grooves in the rock or in the stone walling. The joints between slabs were puddled with yellow clay (sometimes in two layers). There are stones laid on the slabs and the space above them is filled with brash and other small material.

To simplify the matter, it could be said that the problem with flooded cellars was the reason for building a labyrinth of drain passages, which connects almost all the house cellars on the Lower square. Similar system was constructed on the Upper square too, but the two systems are independent of each other. It can be claimed with certainty that the underground is a thoroughly elaborated mine work, which had been built gradually as the problems with ground water had been emerging. It was probably finished in the period of the greatest bloom of the town in the 16th century.

In the same period the town underwent a reconstruction of the buildings in the renaissance style which was not always respectful to the original estate. Renaissance cellars ( so called first floor cellars) are hollowed out above the original gothic ones, and they are affixed with portals with dating back to the 16th century.

The system was kept partly functional during the following two or three centuries. Later, the cellars were gradually getting silted due to the destruction of the moat.

The rising of ground water surface level and consequential flooding of cellars on lower floors was caused by siltation of the drainage system.

According to an archaeological report, in the 19th century the system reached the point of complete siltation and the cellars were partly flooded. Later, some of the renaissance cellars were also flooded as a result of a flood in the area in the 1970’s.

Josef Střecha, a history teacher in the primary school in Slavonice and an enthusiast about local history, got interested in the underground in the 70’s. With his school children, he went through the underground of the museum and the parsonage in the highest part of the system, area, which, unlike other parts, was not entirely flooded yet. He recorded this expedition in his book.

At the beginning of the 90’s, the town hall gave the first impulse to initiate the exploration and sanitation of the town underground. There was little known about the underground at the time, because except Mr. Střecha’s records, no other written records existed.

Sanitation works and mapping out the underground area were initiated in 1993 by various researches ( hydro-geological, geological and archaeological ) and laying process.

The abstersion, caving removal and static securing of the passages itself was proceeded with in 1993. Manual works, at most with the use of winches and pumps.

After clearing several meters of the passages, it was obvious that clearing would involve hard labour, the transportation of mire and sand deposit to the surface being so difficult. The passages were often filled with the deposit up to four fifths of their total height. The assumptions that at least partial mechanisation could be used to clear the passages could not be carried out for the passages are curved, have insufficient visibility and their walls are considerably rough.

After the deposit had been removed, the passages were measured. The part of the underground which has been explored till present day is about 1375 meters wide and is situated 4 – 7 meters under the terrain surface. The cellars were drained and dried up after the clearing. Humidity of the brickwork was gradually reduced and the subsoil of the houses was strengthened. It was verified that passages have a very good natural ventilation thanks to the sloping ( gneiss is weathered to clay minerals, which are firm when dry).

The Lower square system functions today as it did in the middle ages. Using the gravity feeding, the system draws off water through a new drain to the local brook and thus reduced the ground water level. The drain compensated for the function of the defunct medieval moat.

The Upper square system is now being researched and the possibility of drainage is being searched for.

For thousands years, the underground with its mysterious history had been hiding various historical evidence of the life of local inhabitants, which is very valuable not only for the town. History of the underground was up to the archaeologists to reveal as there had been practically no written evidence of the town origin.

While uncovering the original mine shafts, another stone block paving was discovered in the depth of 50 centimetres, and it proved to be older than the one coming from renaissance period. It consisted of smaller silica cobbles, with occasional usage of a quarry stone. Numerous collection of fragments of ceramics, woods and animal bones was gained during works in the underground. There is common kitchen assortment represented in the collection of ceramics ( pot, bowl, beaker, jug, plate and chamber tiles ) coming from the 15th century, and ceramic fragments from the end of the 13th century. Metal objects were also found there, like horse-shoe, nails and a metal gusset used for quarrying.

Archaeological findings are of crucial importance for the underground. They helped to determine the time of origin and the purpose of this truly imposing work of our ancestors.

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