London is one of my favourite cities in Europe and Greenwich is one of my favourite places in London. I've been several times in London, most recently in August 2010, and each time I visited Greenwich. In my view, the Royal Greenwich Observatory is the most beautiful place of the WHS. The view from the observatory to the Queen's House, the Royal Naval College, and the modern office buildings on the Isle of Dog in the background is marvellous (photo). On the roof of the observatory a red Time Ball was installed. This ball is still being pulled up every day and falls down exactly at 1 pm. Once the ships on the Thames used this procedure to set their chronometers to the exact Greenwich Mean Time. The problem of exact time measurement and thus the accurate determination of longitude of a ship at sea and how it was resolved is a major theme of the museum. There you can admire the historic marine chronometers by John Harrison. And of course I stood on the prime meridian and took a photo of my feet.

Also worth a visit are the Painted Hall at the King William Building and the Queen's House with the tulip stairs. Part of the WHS is also the lovely centre of Greenwich with its Georgian and Victorian buildings. And it's funny to walk through the Greenwich foot tunnel (not for people with claustrophobia) to the opposite bank of the Thames. There you can enjoy the view from the Island Gardens to Greenwich.