The observatory was commissioned in 1675 by King Charles II, with the foundation stone being laid on 10 August. British astronomers have long used the Royal Observatory as a basis for measurement. Subsequently, nations across the world used it as their standard for mapping and timekeeping. The Prime Meridian was marked by a brass (later replaced by stainless steel) strip in the Observatory's courtyard once the buildings became a museum in 1960, and, since 16 December 1999, has been marked by a powerful green laser shining north across the London night sky. 82060212
2019 RBC Solutions | Toronto, Canada | photographed: 1982 June
