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Royal Observatory ★★

The popular tradition of standing in two hemispheres along the official Prime Meridian (Longitude 0º) at the Royal Observatory in Greenwich (Photo © Reid Bramblett)
The popular tradition of standing in two hemispheres along the official Prime Meridian (Longitude 0º) at the Royal Observatory in Greenwich

Set your watch by the actual Greenwich Mean Time clock, straddle the Prime Meridian line that divides the eastern and western hemispheres, and tour the fascinating little museum about it all

The Royal Observatory atop Greenwich hill is where they keep the Prime Meridian—well, the marker for it—the line that marks 0° longitude and thus divides the Earth into the eastern and western hemispheres.

Inside are loads of historic scientific devices, including the four clocks, made famous by the book Longitude, that finally helped mariners determine the precise measurement of longitude—the Holy Grail of seafaring for centuries.

A digital clock outside, set right at the Prime Meridian, lets you know down the millisecond exactly what time it is — the original Greenwich Mean Time, by which most of the world sets its clocks.

Also on the grounds are a Planetarium and Astronomy Centre (with a hunk of 4.5 billion-year-old meteorite you can touch)—the only bit of the Royal Observatory that is free anymore.

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Tips

How long should I spend at the Royal Observatory?

Everyone wants to come up here to straddle the hemispheres and set their watches (or at least check their cellphone to see if it does, indeed, have the correct time). Just to do that—and take the photos—takes all of ten minutes.

If you tour the observatory itself, budget another 20–30 minutes or so for a total of maybe 45 minutes.