ABSTRACT: Instead of any recent discoveries, the cases presented support ideas matured along sixty years familiarity with underground works: depending on the depth, the most important factor of success is to find the best fit between the shape and orientation of a cavern on one hand, the anisotropies of the rock mass, and the stress field on the other one. Joints and faults play the first role at rather shallow depth; the behaviour of the rock mass under stress gains more importance with increasing depth. Collection of geological data is indeed the major prerequisite for any cavern design. Means for coping with high stress are recalled. As distance between caverns plays more in situ than into models, groups of caverns may be far less stable than isolated ones. Underground siting of any hazardous depots and activities brings the highest safety level, including for nuclear power plants