Abstract: An inflatable structure comprises a double wall pneumatic envelope including top and bottom panels. The inflatable structure also includes a central mast and a series of peripheral poles. A central portion of the bottom panel is mounted to a top end of the mast, whereas the bottom end of the mast is secured to the ground. The poles are connected at their upper and lower ends respectively to peripheral portions of the envelope and to the ground. An unrestrained lens-shaped double wall envelope submitted therein with pneumatic pressure tends normally to undergo a reduction of its perimeter while its vertical thickens so as to adopt a sphere shape. Mere pneumatic pressure provided in the envelope thus causes the double wall envelope to inflate, the top panel being supported by the pneumatic pressure in an inflated position, whereas the peripheral portions of the envelope are supported, spaced apart from the ground, by the pneumatic pressure and by the poles.