A mooring facility for a tethered gas balloon comprises a building structure containing a hemispherical basin capable of receiving the lower portion of an inflated lighter-than-air gas balloon for mooring the balloon. The surface of the bowl structure is complementary to the surface contour of the lower portion of the balloon. A gondola is suspended beneath the balloon and occupies a central recess in the bowl structure when the balloon is moored. The balloon is tethered by a cable and can be raised and lowered between an elevated operating position and a lowered moored position. The facility avoids the need for a large space requirement and can be erected or installed in a built-up area in or adjacent to a town or city.