Archaeological exploration in Laos has been limited due to rugged and remote topography, a history of twentieth century conflicts which have left over two million tons of unexploded ordnance throughout the country, and local sensitivities to history which involve the Communist government of Laos, village authorities and rural poverty. The first archaeological explorations of Laos began with French explorers acting under the auspices of the École française d'Extrême-Orient. However, due to the Lao Civil War it is only since the 1990s that serious archaeological efforts have begun in Laos. Since 2005, one such effort, The Middle Mekong Archaeological Project (MMAP) has excavated and surveyed numerous sites along the Mekong and its tributaries around Luang Prabang in northern Laos, with the goal of investigating early human settlement of the valleys of the Mekong River and its tributaries.