Portugal's colonial history has long since been a cornerstone of its national identity, as has its geographic position at the south-western corner of Europe, looking out into the Atlantic Ocean. It was one of the last western colonial European powers to give up its overseas territories (among them Angola and Mozambique in 1975), turning over the administration of Macau to the People's Republic of China at the end of 1999. Consequently, it has both influenced and been influenced by cultures from former colonies or dependencies, resulting in immigration from these former territories for both economic and/or personal reasons. Portugal, long a country of emigration (the vast majority of Brazilians have Portuguese ancestry), has now become a country of net immigration, and not just from the last Indian (Portuguese until 1961), African (Portuguese until 1975), and Far East Asian (Portuguese until 1999) overseas territories. An estimated 800,000 Portuguese returned to Portugal as the country's African possessions gained independence in 1975. By 2007, Portugal had 10,617,575 inhabitants of whom about 332,137 were legal immigrants.

What is the cornerstone of Portugal's national identity?