Montjuic sandstone (from the near hill south of the downtown Ba rcelona) has been dominant, and practically only source of rock starting in the foundation of C olonia Barcino (15-10 a.C.) under Augustus in roman times till the starting of XX century. The ma in features of this rock are a good to excellent cementation (essentialy by silica) and a prevalenc e of quartz and silica, secondarily feldspar clasts. The sorting is clasts in general very good, bu t from time to time conglomeratic sandstone was also carved to provide building bloc ks. This resu lts in excellent mechanic properties and high resistance to decay. Last but not least, th e porosity and permeability behavior provide optimal durability in the context of a Mediterranean cl imate. The roman, medieval and modern age walls of the city were built with this material, bei ng the best preserved examples of fortifications some residual bu ildings of the Ciutadella Castle (erected after the 1714 Catalonian defeat), the medieval and postmed ieval sector around the Drassa nes (dockyards) and the Montjuic castle (a little fort built in 1640, then enlarged to fortified castle in two steps, first in 1694, then in 1751-1799), on the top of the hill providing the sandstone. The aim of this communication is to provide petrological and petrophysical data in order to charact erize this type of material so important in the city of Barcelona. ; Peer Reviewed ; Postprint (published version)