Nairobi is the capital city of Kenya and is located in the highlands, near the Tanzanian border. With over 3,000,000 citizens it is the fourth largest city in Africa and home of the United Nations Environment Program. Nearby are two of Africa's eight biodiversity hotspots: the mountains of the Eastern Afromontane and the coastal forests of Eastern Africa. Agriculture has contributed to the growth of the city which, is surrounded by crops and has a very good trade in flowers as well as coffee, tea and cattle. Nairobi is also home to the largest slum of the country - Kibera - also the second largest in Africa.