Discover Greenwich: the place where time begins

The historic Prime Meridian of the world is Royal Observatory Greenwich's most famous landmark. This is the line that divided the eastern and western hemispheres of the Earth, and ushered in the global time system we still use today.

Stand with one foot in the east and one in the west for an iconic photo, then take a tour round the historic buildings to find out how the Observatory found itself at the centre of the world. Time, astronomy, history and navigation – it all comes together at the Royal Observatory.

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Your time in Greenwich doesn't stop at the Prime Meridian line – there's a whole lot more to explore at the Royal Observatory.

Before GPS and smartphones, it was difficult for sailors to know their precise location at sea. While finding their 'latitude' (their position north or south) was possible using the Sun and stars, working out their 'longitude' (position east or west) was harder. 

Carpenter-turned-clockmaker John Harrison held the solution.

His revolutionary 'marine chronometers' (sea clocks) kept accurate time, even while at sea. This accuracy allowed sailors to calculate the difference between their local time and the time in Greenwich. From this they could work out their longitude.

Chronometers based on Harrison's dramatically reduced the risks of travelling by sea. The Royal Observatory became a testing laboratory for these vital instruments, and Greenwich confirmed its status as a centre for global time and navigation.

See the Harrison clocks on display inside the Royal Observatory's dedicated 'Time and Longitude' gallery.

The bright red Time Ball on the top of the Royal Observatory is a distinctive spot on the Greenwich skyline. It also serves a very practical purpose.

The Time Ball was first set up in 1833 as a way for ships moored in the Thames to set their clocks – and it still operates today.

Each day at 12.55pm, the ball rises half way up its mast. At 12.58pm it rises all the way to the top. At 1pm exactly, the ball falls, providing an accurate time signal for anyone who happens to be looking up the hill towards the Royal Observatory.

Greenwich Park is one of London's oldest Royal Parks, and traces of times long gone are everywhere.

Start by enjoying the view from the platform outside the Royal Observatory, comparing the historic buildings of Greenwich's UNESCO World Heritage site with the gleaming skyscrapers of Canary Wharf beyond.

Later, take a picnic into the park and search for signs of the Park's deeper history, from the remains of a Roman temple to the tree that reportedly once sheltered Queen Elizabeth I.

Cutty Sark is the world's sole-surviving tea clipper. Stepping aboard is like stepping back in time, to an era when sailing ships travelled the world and seafarers battled wind and wave to deliver their cargoes as quickly as possible.

Cutty Sark could have been lost to history many times over the course of its long life. Today however, shipkeepers and conservation experts work tirelessly to care for the ship, preserving this maritime survivor for current and future generations.

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