The Royal Observatory, Greenwich, located in London, England, was established in 1675 by King Charles II to improve navigation at sea. It is famous for its role in the development of astronomy and navigation, particularly for establishing the Prime Meridian, which is the reference line for longitude. Today, the observatory houses a collection of historical telescopes and instruments, along with a museum that showcases the history of timekeeping and navigation. Visitors can explore the grounds, see the iconic Greenwich Mean Time (GMT) line, and learn about the contributions of notable astronomers like Sir Christopher Wren and John Flamsteed.