Peru is the third-largest country in South America, located on the west coast of the continent, just south of the equator. The country has three main geographic zones: the Andean highlands, the desert coast and the largely unpopulated Peruvian Amazon. Pre-colonial civilization in Peru was centered on the rugged Andean highlands, where most of Peru's natural riches — including gold, silver and hydrocarbons — are concentrated. The arrival of European colonists and maritime transport focused economic and political activity on the coast, and eventually created the modern state of Peru, with Lima as its capital. This metropolitan area produces more than 50 percent of Peru's gross domestic product (GDP) and is home to a third of the nation's population. With the Andes protecting Peru's coastal core, Peru's biggest external threats have come from the north, the south and the sea.