The Royal Observatory Greenwich, founded in 1675 by King Charles II, is known as the home of British astronomy. At the home of space and time, you'll learn all about the Greenwich Mean Time (GMT), and how the search for a way to measure longitude led it to be the Prime Meridian of the world back in 1884. Situated on a hill in Greenwich Park in southeast London, it overlooks the River Thames to the north and is surrounded by a picturesque view, including that of the Queen's House.