Museum of time and space, built by Sir Christopher Wren in 1675, and site of the Greenwich Meridian. This is the base point for world time and the site of Longitude 0 where you can watch the timeball drop at 1300 each day. Visitors can see the Astronomer Royal's apartments, the famous Harrison timekeepers (1735-60) with computer simulations, intricate instruments, Wren's Octagon Room and the largest refracting telescope in Britain.