- What you can expect - 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. - Important Info - Child policy: - Children under 4 years are free of charge. - Children under 16 years must be accompanied by an adult. Good to know: - Check the official website for the daily opening hours and closure dates prior to your visit. - The interactive, multilingual audio guide can be downloaded on your smartphone using the Smartify App. - Entry to Queen's House and National Maritime Museum is free of charge, except for special exhibitions and guided tours.