On July 9, 2011, the Republic of South Sudan became the newest nation in the world, six months after its declaration of independence from Sudan. Juba, a port city on the White Nile, is the capital of the new nation and is one of the fastest growing cities in the world. The city has doubled in size since 2005, when a peace agreement ended the civil war in Sudan. Both hopeful immigrants and returning residents have created the population surge. The city was a central point for humanitarian aid, and the operations base for the United Nations and non-governmental organizations during the Sudanese conflicts. Today, a significant number of foreign aid workers remain in the city. During the conflict, city infrastructure and main transportation arteries suffered heavy damage. The city is still surrounded by army camps and squatter settlements (labeled "informal built-up areas" in the image). They appear as muted gray areas extending outward from the center of the city.