Stand on the Prime Meridian Line

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Location	Royal Observatory
Price	Included with entry to the Observatory
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Stand on the historic Prime Meridian of the World at the Royal Observatory Greenwich.

Since 1884, all distances east and west have been measured from the Prime Meridian line in Greenwich.

Astronomers at the Royal Observatory took thousands of measurements to define the Prime Meridian and establish zero degrees longitude. In an age before smartphones and satellites, their work transformed how we explored our world.

Come to Greenwich and follow in their footsteps. Visit the Royal Observatory, walk along the line where east meets west, and discover the history of time and space.

What's so special about the Prime Meridian line?

Since the late 19th century, the Prime Meridian at Greenwich has divided the eastern and western hemispheres of the Earth - just as the equator divides the northern and southern hemispheres. When you stand across the line, you have one foot in the east and one in the west!

The Greenwich Meridian also helped to establish the world time zone system we still use today.

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What is a meridian?

A meridian is an imaginary line running north to south that is used as a reference line for astronomical observations. Meridian lines also help to plot locations here on Earth by offering a way to determine longitude.

Why is the Prime Meridian in Greenwich?

Until the 1880s, countries used their own meridian lines for mapmaking and navigation. This meant there was no globally agreed way of measuring distances and plotting locations east and west.

In 1884, different nations gathered in Washington D.C. to choose one single meridian as a common reference. After weeks of discussion, delegates voted to make the Greenwich Meridian the world's Prime Meridian.

Greenwich was chosen because its measurements were already used by most of the world's seafarers and mapmakers. Thanks to the work of generations of astronomers, the Royal Observatory became the home for global time and navigation.

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How many countries does the Prime Meridian pass through?

From pole to pole, the Prime Meridian covers a distance of 20,000 km.

In the northern hemisphere, the Prime Meridian passes through the UK, France and Spain in Europe, and Algeria, Mali, Burkina Faso, Togo and Ghana in Africa. The only land crossed by the Meridian in the southern hemisphere is Antarctica.

In Greenwich the Prime Meridian is marked by a metal line fixed into the Royal Observatory courtyard, and at night by a laser beam. Depending on the weather, the beam can be seen from more than 20 km away.

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What else can I do at the Royal Observatory?

From John Harrison's revolutionary timekeepers to the Great Equatorial Telescope, the Royal Observatory is home to some of the UK's most prized scientific instruments. See them all on display as you walk round the historic buildings.

The Meridian Courtyard also offers some of the best views in London, high above the trees of Greenwich Park.

Finally, did you know that astronomers still work at the Royal Observatory today? Join them on an inspiring journey into space at London’s only planetarium.

Discover Greenwich: the place where time begins

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Visiting the Prime Meridian in Greenwich

Do I need tickets to visit the Prime Meridian?

The Prime Meridian is included as part of your visit to the Royal Observatory Greenwich. We recommend booking tickets online in advance to guarantee entry and receive updates before your visit.

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Learn more about planning a visit

Getting to the Royal Observatory

The Observatory is located on a hill in the heart of Greenwich Park, close to Greenwich's historic town centre.

Greenwich is a quick, easy journey from central London via train, DLR and bus. Alternatively there is a secure car park nearby at the National Maritime Museum which is open to visitors during weekends, bank holidays and school holidays. Spaces can be reserved in advance when booking tickets.

Check our travel pages for more information about getting to the Royal Observatory as well as other Royal Museums Greenwich sites.

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Where is the Prime Meridian in Greenwich?

The Prime Meridian stretches all round the world! But if you want to stand on the line marked out inside the Royal Observatory itself, head towards the Meridian Courtyard.

This is the historic heart of the Observatory, surrounded by the Meridian Observatory – home to the telescopes that helped define zero degrees longitude – and Flamsteed House, the oldest part of the Observatory.

Follow the audio guide

Learn more about the history of the Royal Observatory and its status as the home of Greenwich Mean Time with the dedicated audio guide, available to all visitors.

Listen to the tour online using your phone or via the Smartify museum app.

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Make the most of your Royal Observatory visit

Find more things to do at the Royal Observatory here.

If you want to see more of Greenwich's historic attractions, book a Greenwich Day pass. This ticket gives you entry to both the Royal Observatory AND historic ship Cutty Sark, with 25% off the standard admission price. Book now