Elliptical dome

[1] Technically, an ellipsoidal dome has a circular cross-section, so is not quite the same.

While the cupola can take different geometries, when the ceiling's cross-section takes the form of an ellipse, and due to the reflecting properties of an ellipse, any two persons standing at a focus of the floor's ellipse can have one whisper, and the other hears; this is a whispering gallery.

[2][3][4] Elliptical domes have many applications in architecture; and are useful in covering rectangular spaces.

[5] In a geodesic dome with a circular base, the triangular elements align so their edges form great circles.

Due to its mathematical derivation, this design is called "geotangent".