ABSTRACT
In the historic centre of Salamanca, declared a United Nations Educational, Scientific and Cultural Organization World Heritage Site in 1988, one can find historic buildings and monuments with their basement constructed using ashlars of different lithological nature. Their state of conservation depends on the kind of stone used. Some bottom ashlars were built with Salamanca sandstone, which is in fact conglomerate containing siliceous cement that decreases its water absorption capacity. Impressive buildings were constructed during the eleventh and thirteenth centuries, most historical buildings in Salamanca were built between the fifteenth and nineteenth centuries. Granite is used as the main construction material for the lower courses, while, in the upper part, Villamayor sandstone is always found. Salamanca sandstone is also found in the bottom ashlars of some buildings, and this is the most difficult material to replace because all historical quarries are currently inactive.
