Bwindi Impenetrable National Park is situated in Uganda, Africa. Thanks to its exceptional biodiversity, with many endangered species such as the gorilla, the park was declared Unesco's heritage in 1994. Its vegetation is mainly made up of tropical rainforest or jungle, along with some mountainous areas. Its ecosystem is one of the most complex in Africa and the area derives its name frome the fact that the forest can be reached only on foot and with extreme difficulty. It is home to 120 mammal species, 346 bird species and 202 types of butterflies. The gorillas in the park, known as Bwindi gorillas, are divided into four groups, three of which are completely free and one is controlled by research projects of the scientific community.