This paper summarizes test results obtained during the so-called “Test Cavern” project performed in the salt mine Bernburg (Saxony-Anhalt, D) aiming on the long term behaviour of a sealed brine filled cavern. Because its evolution depends on the system’s geomechanical and hydraulic properties and their interactions, an extensive research program were done comprising in-situ tests in a brine filled model cavern and bore holes, rock mechanical investigations and modelling. Only for the purpose of well defined test conditions and for facilitating a latter direct inspection of the brine pressure affected rock wall a model cavern with a total volume of around 22 m³ was leached of at an underground level of around 420 m. Major part of the research program were the pressure build up tests performed as well in the test cavern and as well in boreholes for over a duration of 2.5 years allowing an estimate regarding scale effects. With respect of interpreting the in situ results an accompanying rock mechanical investigation program was carried out to prove the deformation behaviour of the surrounding rock mass, the stress state in the solid by hydro-fracturing and the rock mechanical behaviour of rock salt samples from the surrounding rock mass. Finally, the observed time dependent coupled processes were numerical modelled using a modified FLAC-Code allowing the quantitative simulation of pressure dependent brine permeation in into the wall.