The Monuments of Portugal were constructed throughout the Portuguese territory, and date back to the period of pre-historic settlement of occupation. Subsequently, the region that is today Portugal has been colonized by many civilizations, which have left marks in the territory, constructing markers, defensive structures, homes and places of worship to suit their requirements and means. The formal organization of the Portuguese state resulted in a process to qualify and quantify those structures that have had an intrinsic value to the Portuguese culture. Starting with the Direcção Geral dos Edifícios e Monumentos Nacionais (DGMEN), and later by the Instituto de Gestão do Património Arquitectónico e Arqueológico (IGESPAR), the Portuguese government developed a registry of national monuments that includes a rich heritage of historical monuments throughout the country. This is a compilation of those structures that are designated as National Monuments (Portuguese: Monumentos Nacionais) only.