It is located in the center of the province and its landscape is dominated by mountains and low vegetation.

It is bordered by: Ullum is entirely located on the center and foothills of the San Juan Cordillera.

Between the mountains are prominent hills: the Lomadas de Las Tapias, Talacasto, Dehesa and Villicum to the east and the Sierra del Tigre and Sierra de la Invernada to the west.

The climate is influenced by the Ullum dam lake and by occasional snowfall in the Talacasto area.

The fauna includes species such as hares, puma, viscachas, Elegant Crested Tinamous, guanacos, various forest birds and silversides.