At , Rwanda's population density is amongst the highest in Africa. Historians such as Gérard Prunier believe that the 1994 genocide can be partly attributed to the population density. The population is predominantly rural, with a few large towns; dwellings are evenly spread throughout the country. The only sparsely populated area of the country is the savanna land in the former province of Umutara and Akagera National Park in the east. Kigali is the largest city, with a population of around one million. Its rapidly increasing population challenges its infrastructural development. According to the 2012 census, the second largest city is Gisenyi, which lies adjacent to Lake Kivu and the Congolese city of Goma, and has a population of 126,000. Other major towns include Ruhengeri, Butare, and Muhanga, all with populations below 100,000. The urban population rose from 6% of the population in 1990, to 16.6% in 2006; by 2011, however, the proportion had dropped slightly, to 14.8%.