4Royal Observatory, Flamsteed House and the Meridian Courtyard

The home of Greenwich Mean Time, with the Prime Meridian line, the Harrison timekeepers, the Octagon Room and the time ball.

In This Area

The Prime Meridian Line

Defined by George Biddell Airy's transit circle, Transit circle 1850; adopted internationally 1884

Royal Observatory, Meridian Courtyard and Meridian Building

Harrison's First Sea Clock, H1

John Harrison, 1730 to 1735

Royal Observatory, Flamsteed House, Time and Longitude gallery

Harrison's Prize-Winning Watch, H4

John Harrison, 1759

Royal Observatory, Flamsteed House, Time and Longitude gallery

Flamsteed House and the Time Ball

Christopher Wren, with Robert Hooke, 1675 to 1676; time ball added 1833

Royal Observatory, Flamsteed House, northern edge of the site

The Shepherd Gate Clock

Charles Shepherd, 1852

Royal Observatory, wall beside the main entrance gate