Citadel. The citadel is an elevated, fortified region that overlooks the rest of the city. It was most likely the residence of the local kings. The fortress contained a pool known as the Great Bath, which was most likely utilized for religious events. Citadels are commonly found in medieval and early modern Europe where they were used to protect cities from invasion or attack. They could be found within urban centers or alongside major roads outside protected walls. Sometimes they were even built into mountains! In India, the term citadel refers to any large townhouse or mansion built by a wealthy person. These buildings usually have high walls around them, with only the main entrance being on the ground floor. The interior rooms are also very large compared to other houses in rural India, measuring 20 feet by 30 feet (6 m by 9 m). There are several such buildings in Mumbai (then called Bombay), including those owned by the Tata family, the Jamnadas Bhawalkar family, and others. Citadels first came to India when Arab traders built ones in various Indian ports to protect themselves from piracy. This kind of fortress continued to evolve in India too, where the Arabs introduced heavy artillery which made these defenses necessary. By the 16th century, Mumbai had become one of the largest trading cities in the world and needed better defense systems.