a1_A water-tube tiltmeter system composed of two perpendicular tubes was installed in the underground galleries of the Geodynamic Laboratory in the Książ Castle, Central Sudetes, in 2003. The partially filled water tubes are several tens of metres in length and have high-precision interferometric recording gauges at their ends. The recording gauges continuously measure water level changes in the tubes with single-nanometer accuracy which corresponds to 0.005 milliseconds of arc of plumb line variations. The tiltmeter has recorded several events of water level variations, with a magnitude of a few hundred micrometers and a duration of tens of days. The strongest water level variations were one order greater than variations caused by tidal phenomena and occurred in different months of a year, and hence are expected to have no seasonal origin. Because of the extremely large magnitude of the phenomenon and because time of duration of signals showed no seasonal characteristics, all external sources outside the bedrock space occupied by the instrument can also readily be precluded. Each of the recorded strong signals of water level variations consists of a symmetrical and an asymmetrical component. Because of the proportion of the water system to the large-scale geodynamic sources producing water level changes, all the external geodynamic reasons can generate only symmetrical signals in the tubes. The evidence indicates episodic tilting of the instrument itself or vertical displacements of any part of the tubes, which supports the notion of active bedrock deformation. The combination of symmetrical and asymmetrical signals implies that their source is within the bedrock space in which the instrument is embedded. The events of large water level variations can be explained by non-flat relative vertical displacement of the opposite ends of the tiltmeter tubes., a2_Asymmetrical signals are particularly pronounced in the tube named 03-04, and their magnitude suggests vertical displacement of part of the tube of the order of hundreds of micrometres. The repeatability, temporal irregularity, considerable duration time and high magnitude of the strong signals lead us to attribute them to the tilting of tiltmeter bedrock due to contemporary tectonic movements of the Książ Massif. The Książ Massif consists of a rigid rock mass of Famennian−Tournaisian conglomerates cut by several large and small faults. Rock compaction can be precluded. The massif is a prominent bedrock spur carved by a deeply incised river, and its geomorphic development seems to be related to major faults. Preliminary geological study has recognized strike-slip faults, thrusts and extensional fracture zones, some with an indication of recent activity. A few minor faults cross the bedrock under the tiltmeter geodynamic system. The tiltmeter is thus likely to be recording local signals of neotectonic activity., Marek Kaczorowski and Jurand Wojewoda., and Obsahuje bibliografii