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. Although Peru has had border disputes with both neighbors Ecuador and Colombia, Peru's main rivalry is with Chile. In the late 1800s, Peru and Chile fought the War of the Pacific. During that war, Chile seized large portions of the Bolivian and Peruvian Atacama Desert using its significantly more powerful navy. But Peru's biggest challenges by far come from its internal security situation. Deep ethno-linguistic divides between European descendants and Aymara, Quechua and other Andean communities are exacerbated by rugged terrain and poor infrastructure. As a result, civil unrest is pervasive and frequently violent. At the same time, Peru is the native home of the coca plant, which brings regional drug trafficking networks deep into the heart of Peru in pursuit of cocaine supplies. In turn, this fuels drug related violence and funds armed rebel groups. Despite these challenges, Peru has seen significant growth in recent years. However its basic geography will give the country an internal focus for the foreseeable future.