Gabriel's horn is the surface obtained by revolving the graph of <math>y = 1/x\,</math> for <math>x \geq 1</math> about the <math>x</math>-axis. It is noteworthy for having infinite area, but enclosing a finite volume (in the region with <math>x \geq 1</math>) of <math>\pi\,</math> cubic units.