I saw the Royal Observatory. On top of it is an orange time ball. Every day at 12:58 the ball rises, and exactly at 13:00 it falls and all the navy ships on the Thames set their clocks accordingly. There was a women who used to sail to Greenwich every day and set her watch, and then sailed back to London and sold the correct time there. Until the 19th century there was a different time to each part of England (and the world) - the city time (the time in the city's clock tower) was set according to sundial, and there is a big difference between one area to another, and so Every evening the clock at Oxford's Christ's Church rings 101 times (that's the number of the original students) to call the students in - but it rings at 21:00 Oxford time which is 21:05 London time (and now all England Time).
The reason there is a Royal Observatory in Greenwich is also interesting. Originally the Royal Astronomer sat in the Tower - but the ravens in the Tower kept disturbing his work so he went to the king and the king told the Beefeaters to get rid of the Ravens, but they told him, that there is a legend according to which if the ravens ever leave the Tower the monarchy would fall - so the King sent the Astronomer to Greenwich instead. I think they didn't like the astronomer.
After the tour I ate lunch in a restaurant called Goderd's which is there since 1890, and serves typical English food - especially pies, but also Eel's Jelly. I had a nice pie, and for desert Rhubarb Pie.
Through the Observatory passed the 0 Meridian and there is an exhibition about measuring time and the Meridian Conference.
Then I went to the *National Maritime Museum, which is very big - I spend there an hour but there is at least 3 hours worth of seeing. I saw some of the ship�s models, an exhibition about pleasure cruises with models of cruise ships and recreation of rooms on cruise ships. I even saw the uniform of Nelson from the Battle of Trafalgar.
I took the Dockland Light Railway back to the city.
Links: London walks
The National Meritime Museum
The Cutty Sark
The Royal Greenwich Observatory
Start: Tower Hill Tube (Circle or District Line)
End: Cutty Sark DLR (Dockland Light Railway)