The Royal Observatory in Greenwich adjoins the Peter Harrison Planetarium and visiting both attractions makes for a great day out.
Originally known as the Old Royal Observatory from 1957 to 1998, when the working Royal Greenwich Observatory, RGO, moved from Greenwich to Herstmonceux, the observatory is situated at the end of a long (but pleasurable) hill walk in Greenwich Park, overlooking the River Thames.
The Royal Observatory played a major role in the history of astronomy and navigation and is probably best known for the fact that the prime meridian passes through it, and thereby gave its name to Greenwich Mean Time.
This museum certainly packed in the visitors with plenty of time-keeping, astronomical and navigational apparatus on display. I particularly found clocks used by the BBC back in the early days of the GMT time signal of interest and it was even nostalgic to hear the speaking clock telling us the time over a loudspeaker!
Similar to the Cutty Sark, there were audio guides to navigate your own journey through time, making the visit educational and informative, and again all included with the Royal Museums ticket deal which is great value.