Royal Greenwich Observatory

The Royal Greenwich Observatory, originally built as a workplace for the Astronomer Royal, is located on a hill in Greenwich, south-east of London. The Prime Meridian, to which longitude refers, goes through the observatory.

The observatory was commissioned in 1675 by King Charles II and designed by architect Christopher Wren.

Greenwich Mean Time was at one time based on the time observations made at the Royal Greenwich Observatory, before being superseded by Coordinated Universal Time. While the Royal Greenwich Observatory no longer hosts a working astronomical observatory, a ball still drops daily to mark the exact moment of noon, and there is a good museum of astronomical and navigational tools.