These table-top hills are located to the south of Somontano. Before the Alpine orogeny occurred, sediments of different matter settled horizontally and, layer by layer, built up a stratum of diverse compositions. (limestone, clay, loam etc.) Later, the erosive effects of a network of rivers gave rise to these distinctive hillocks. They are all that remains of a large surface area and now sit isolated between wide valleys that were patiently carved by the erosive force of the rivers.