Through a comparative study of two similar fortifications in their geometric and defensive characteristics, this paper gives a description of each of them on a historical narrative that allows specifying how the processes of transformation and adaptation of buildings was given continuously, like a single project it were , away from the traditional model usually think that American fortifications were a simple adaptation of which were built in Spain . Keywords : Cádiz, Cartagena de Indias, Ignacio Sala, fortification. DOI: http://dx.doi.org/10.4995/FORTMED2015.2015.1675