Progress in cloud physics has been seriously limited because of the impossibility of conducting controlled cloud experiments on a sufficiently large scale. To meet the requirements, a laboratory has been built in which thick artificial expansion type clouds may be produced under controlled and measurable conditions.A mine shaft 0.210 kilometer deep and 2.2×2.2 meters in cross section has been sealed and adapted to the production of thick artificial clouds. The shaft and its principal auxiliaries necessary for the study of some of the basic problems of clouds and precipitation are described. Dense, thick clouds completely filling the shaft are now being produced on a routine basis. Some preliminary illustrative data are presented.