San Pedro cliff is a dihedral 65.5 m high, which has progressed to place itself at 23.8 m from the Alhambra wall-palace that is a heritage of the Humankind. A deep research on the Tectonics of the zone, and an insight into the topographic measurements taken during several years, has shown that active normal faults surrounding the cliff have created an extension tectonic regime that loosens the ground and activates the ground falls. One major fault coincides with one of the faces of the dihedral. The factor of safety of the cliff subject to the 100 years period earthquake is 0.73. The preservation solution proposed is a post-tensioned high elastic limit wire mesh and autochthonous vegetation. With this reinforcement, the factor of safety under that earthquake raises to a value around one. In this way, the environmental impact is negligible.