Nizam of Hyderabad, changed Ulwul's name to Secunderabad after himself. The city was formed in 1806, after the order was signed by the Nizam allotting the land north of Hussain Sagar to set up the British Cantonment. The twin cities are separated by the man-made Hussain Sagar lake, which was built during the reign of the Qutb Shahi dynasty in the 16th century. Unlike Hyderabad, the official language of Secunderabad was English. Secunderabad was exempted from customs duty on imported goods, thus making trade very profitable. Various new markets such as Regimental Bazaar and General Bazaar were created. After the First War of Indian Independence of 1857, the construction of a wall was started at Trimulgherry and completed in 1867. Secunderabad Junction railway station, one of the largest in India and the zonal headquarters of South Central Railway, was established in 1874. The King Edward Memorial Hospital, now known as Gandhi Hospital, was established in 1851. A civil jail (now a heritage building known as Old Jail complex near Monda Market) was also established. Originally constructed in 1860 as the country house of the British Resident at Hyderabad, the Residency House is now known as the Rashtrapati Nilayam, the official retreat of the President of India. Sir Winston Churchill, the prime minister of the United Kingdom during World War II, was posted in Secunderabad during the 1890s as a subaltern in the British Army. Sir Ronald Ross conducted his initial research on the cause of malaria in the city of Secunderabad. The original building is today called the Sir Ronald Ross Institute and is located on Minister Road. Secunderabad Municipality was first formed in 1945. Later in 1950, along with Hyderabad Municipality, it was upgraded to Secunderabad Municipal Corporation under the Hyderabad Corporation Act, 1950. In 1960, by the Hyderabad Municipal Corporation Act of 1955, Secunderabad Municipal Corporation was merged with Hyderabad Corporation to form a single municipal corporation. Today Secunderabad is part of the Hyderabad district. Post-Independence, the Secunderabad Cantonment Board came under the jurisdiction of the Indian Armed forces. Consequently, large military units were established. The popular neighbourhoods in Secunderabad are Paradise Circle, Trimulgherry, Jawaharnagar colony, Marredpally, Jeera, General Bazar, Sitaphalmandi, Kharkhana, Ranigunj, and New Bhoiguda. Begumpet Airport is close to Secunderabad and served the twin city until early 2008. Geography Situated in the North of Hyderabad at ., Secunderabad lies on the northern part of the Deccan