The effect of the operating conditions (base angle, air inlet diameter, stagnant bed height, particle diameter, and air velocity) on the fountain geometry (height and amplitude) has been studied. Likewise, particle ascending and descending zones in the fountain have been delimited. These studies have been carried out by means of an optical fiber and by an image treatment system. An equation has been proposed for the calculation of the fountain height from the vertical component of the particle velocity in the axis at the base of the fountain. The contactor base angle has a major incidence on the fountain geometry. The external diameter of the fountain and that of the core are conditioned by the diameter of the spout at the base of the fountain. The diameter of the core (or ascending zone) decreases with the fountain level for all experimental conditions.