Obélisque de la Concorde serves as a giant sundial in the heart of Paris

In Paris, some monuments hide a surprising function. The Obélisque de la Concorde not only displays hieroglyphs, it can also tell the time thanks to its shadow. For those who look up and observe the square, the experience is simple, precise and poetic.

An Egyptian giant in the heart of Paris

Erected at the center of the square, the Obélisque de la Concorde comes from the temple of Luxor. Donated by Egypt in the 19th century, it was erected in Paris in 1836 under Louis-Philippe, after a spectacular journey.

The granite monolith measures around 23 metres and weighs almost 227 tonnes. In 1998, a golden pyramidion was added to its top, recalling the original lustre of ancient obelisks.

The square remains a lively, historic crossroads. Yet it also serves as the stage for an open-air scientific experiment, invisible until the sun casts the right shadow.

“When the shadow lengthens and touches the landmarks, time takes shape on the stone.”

An urban-sized sundial

An obelisk naturally behaves like a gnomon. When the sun shines, its shadow slides across the markers on the ground, forming a large sundial.

These markers were drawn up at the end of the 20th century with the help of specialists, notably from the Paris Observatory. What’s more, they represent hourly and seasonal lines that help us to read reliable solar time.

• Locate the numbers and metal markings integrated into the keypad.
• Observe where the tip of the shadow falls on a clear day.
• Remember: the time read is solar time, not legal time.
• Add a daylight saving time offset if required.
• Take a photo from the same point at solar noon for comparison.

How to tell the time without a watch

Arrive on a clear day, then turn north. In the middle of the day, the shadow is almost aligned with the north-south axis; reading becomes more intuitive.

Approach the markings in figures. This way, when the tip of the shadow touches a marker, you’ll have the local solar time to within a few minutes.

The difference with your phone comes from the time zone and the equation of time. As a result, the reading varies according to season and date, but the logic remains stable.

From sunshine to legal time: fine tuning

To switch from solar time to legal time, add the time zone offset. In France, the basic difference is about one hour, then one hour more in summer.

There’s also the equation of time, due to the Earth’s orbit. So, depending on the month, we can gain or lose up to fifteen minutes on average solar time.

Historical landmarks and engineering details

The monolith bears hieroglyphs celebrating Ramses II. Its base also recounts the epic story of transportation, a technical feat orchestrated by 19th-century engineers.

The golden top shines to compensate for the loss of the antique capstone. Also, this modern piece improves shadow visibility, without betraying the original aesthetic.

The ground hourds have been calculated for the latitude of Paris. In short, they take account of the seasons, so that the shade remains a readable indicator all year round.

One monument, many readings of time

The Obélisque de la Concorde speaks of both Egypt and Paris. Thanks to the sundial, the monument links solar cycles to contemporary daily life.

In the morning, the shadow lengthens towards the west; in the afternoon, it lengthens towards the east. In this way, the same walk tells a different story depending on the time of day.

Tips for a successful visit

Choose a sunny day with little wind. Then stand at a distance so that you can see the tip of the shadow touching the markers.

Keep an eye out for traffic, as the square remains a crossroads. However, slight movements are often all that’s needed to compose a clear, confident picture.

On site, take the time to read the base and reliefs. As a result, you connect technical data with sensations, in front of the Obélisque de la Concorde, which plays the role of urban watchmaker.

Knowing more about the method makes it easier to read. So, take a small notebook, write down the solar time you read, then compare it with legal time.

This gap game invites you to understand the Earth and its path. What’s more, it turns a stroll into an open-air science session.

Families appreciate this hands-on experience. It’s also a free and stimulating support for teachers and mediators.

The monument benefits from regular maintenance, particularly for the gilding. In short, this care ensures a clean shadow, useful for the giant sundial.

Finally, the site remains accessible almost all day long. As a result, the light changes and renews the readings, from morning to night.

This heritage tells the story of an ongoing Franco-Egyptian dialogue. The Obélisque de la Concorde, for example, combines art, history and science in a single square.

Faced with the sun, everyone becomes an observer of time. What’s more, a simple shadow reminds us that the city breathes to the rhythm of the stars, without noise or mechanism.

• Concorde Obelisk