Archaeological studies in and around Bangui have yielded at least 26 ancient Iron Age sites that contain many metallurgical tools and objects, illuminating the pre-European history of the city and surrounding area. The archaeological sites were added to the UNESCO World Heritage Tentative List on 11 April 2006 in the Cultural category. The site closest to Bangui is Pendere-Sengue,  from Independence Avenue, where archaeologists and conservation agencies have carried out studies. It is a paleo-metallurgical site where several thousand shards of ceramics, iron tools, pottery, and an iron spatula weighing  have been unearthed. Its dating, compared with similar sites in Nigeria and Sudan, could be close to the 9th century BC.