Abstract: An inflatable structure for totally enclosing a predetermined area such as sports ground, swimming-pool and the like comprises a flexible envelope having a single or double wall which is placed during service over the area to be protected and a base which is anchored to the ground. The envelope is maintained in the distended condition during service by a pressure which exceeds atmospheric pressure. The wall or walls of the envelope are each joined to the base by means of a detachable assembly device such as a zipper-type slide fastener which permits assembly or disassembly of each wall independently of the other.