Cupola

Cupola (through Ital. fr. Lat, cupa, tub, cask), originally a semi-spherical dome, such as that of the Pantheon at Rome, or the temple of Vesta at Tivoli; and later and more generally a modified form, generally a semi-ellipse. More loosely the name is applied to any rounded top; in naval architecture to the revolving gun-turret on some kinds of ironclad; and it is used in conchology to denote the bulge of a shell.