| Summary: | The carbonate stones that make up the four fountains of the 18<sup>th</sup> century located in the<em> Paseo del Prado</em> of Madrid (Spain) are studied. The documentary search in historical archives, together with the petrographic, cartographic and paleontological studies permitted to determine that the fountains have been built with dolostone of the <em>Castrojimeno</em> Formation, with gastropods of the Trochactaeon Lamarcki specie of the Santonian (Upper Cretaceous). The historical quarries from which the ashlars have been extracted is located in <em>Redueña</em> Village. The petrophysical properties of this dolostone (effective porosity, bulk density, mercury intrusion porosity, ultrasound wave propagation velocity, micro-roughness and color) have been calculated and compared with <em>Colmenar de Oreja</em> limestone. Each of the four fountains has a circular pylon at the base, a central column that holds a smaller pylon and is topped by a sculpture that serves as a spout. A bomb destroyed three ashlars of the basal pylon, column, small pylon and the sculpture of the SE fountain, during the Spanish Civil War, in 1936. These damaged elements were replaced by other carved limestones from<em> Colmenar de Oreja</em> in 1944. The four sculptures had been replaced in 1996 with resin replicas and the originals are preserved in the <em>San Isidro. Los orígenes de Madrid</em> museum. The study of the petrophysical properties of the sculptures located in the museum allowed us to determine the decay of different stone types. The analysis of micro-roughness was employed to define that the dissolution effect on the sculptures is different between dolostone and limestone. <em>Redueña</em> dolostone is more resistant to dissolution effect than <em>Colmenar de Oreja</em> limestome.
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