to assist with their commercial vessels. To this day Kilwa Masoko remains the capital of Kilwa district. During the British occupiation the district was one of six councils established in 1947 in lindi region. Post independence, in 1984 Kilwa was officially designated as a district council. Geography Kilwa district is the second largest district in Lindi region. It has a total area of 13.347.50 square kilometers, of which 12,126 square kilometers is land and 1,221.25 square kilometers is water. Kilwa district has 5 Islands, with the largest one being Kilwa Kisiwani. The other islands in the Kilwa archipelago are [Kati Island] and Songo Mnara Island. In addition, the Songosongo Islands archipelago is composed of 21 coral reefs including the 4 coral islands. The four Islands in the archipelago are Fanjove, Nyuni Island, Songo Songo and Okuza Island. Kilwa District is home to Pindiro Forest Reserve where albino hippopotamuses have been observed. The soil structure of Kilwa district is of low fertility is mostly made of well-drained, low-moisture retaining sedimentary sandstone. The [[Matandu River]] is the largest river running west to east of Kilwa district. The other rivers found in the district are the Mbwemkuru River, Matandu River and the Mavuji River. There is also a cave system in Kipatimu ward, the Nan'goma Cave. The cave system is located in the Matumbi Highlands which are shared between Kilwa District and Rufiji District in Pwani Region. The climate of Kilwa District is a tropical Savannah climate with an average annual temperature range of 22 degree Celsius to 30 degrees Celsius. The annual precipitation is between 800 and 1400 millimeters per year. The north of the district being far wetter than the south with the former receiving an annual rainfall of 1000 to 1400mm. The latter receives around 800 to 1400 mm per year. Demographics According to the 2012 Tanzania National Census, the population of the Kilwa District was 190,744. of which 91,661 were male and 99,083 were female. Most residents of Kilwa district practice Sunni Islam. In Lindi Region, Kilwa district has the average highest household size of 4.4. As mentioned in the history section of this article Kilwa district is the ancestral home of the Mwera, Matumbi and Machinga people. Most of the population has been Swahilized and speak Swahili as their first language and practice Swahili culture. However, many elderly and people living in rural areas speak their native languages.