Red-light district
A red-light district is a neighborhood where prostitution is common. The term was first recorded in the United States around 1890, and derives from the practice of placing a red light in the window to indicate to customers the (often illegal) nature of the business.Interestingly, one of the many terms used for a red-light district in Japanese is akasen (赤線), meaning "red-line district".
Famous Red-Light Districts