Abstract: A waterborne building structure is disclosed comprising a floatable bottom portion generally formed as a hemisphere having a downwardly protruded portion at its lowest end and a disk-shaped upper portion of horizontal form with gradually widening width and vertical supporting walls exposed to the water surface at its uppermost side, pillars extending from said lowest end vertically to a height above said bottom portion approximately equal to the diameter of said upper portion, cables extending from an upper portion of said pillars in a radial form to said supporting walls, prefabricated rooms affixed to said cables arranged in circular form having ventilation spaces between said rooms, first joint spaces with windows in said rooms, second joint spaces in said floatable bottom portion having windows in contact with the water, and third joint spaces arranged in the uppermost portion of said structure.