One of Florence’s greatest spectacles is about to begin

Each June, Florence Cathedral hosts a unique demonstration of nature's precision matched by human engineering: the passage of the midday sun through a gnomon set into the mighty dome.

One of Florence's greatest spectacles is about to begin
The dome of Florence Cathedral. Photo: Giuseppe Cacace/AFP

Unnoticed by visitors for most of the year, the Duomo's gnomon – a device that tells the time of day or year by the way the sun strikes it – comes into its own between late May and July each year.

The instrument itself is hard to spot: located just over 90 metres up, just beneath the windowed lantern at the top of the dome, it looks like a small bronze shelf jutting out from the southern wall.

Photo: Sailko, CC BY-SA 3.0, Wikimedia

More easily identified is the brass meridian line running across the floor of the Chapel of the Cross, accompanied by an inlaid circle.

But what's it for?

That question is answered at midday on June 21st, the date of the summer solstice when the sun is at its highest point in the sky. It's then that light hits the gnomon, which has a round hole in its centre, and is projected along the meridian and onto the circle, which matches it perfectly in size.

Photo: Sailko, CC BY-SA 3.0, Wikimedia

The device is what's known as a pinhole gnomon, which means that instead of casting a shadow the way the simplest sundials do, it projects a circle of light – a miniature image of the sun. 

This image moves with the real sun across the sky (or rather, with the earth as it rotates and makes the sun appear to be travelling). It can be seen sliding down the walls of the cathedral and across the floor for several weeks when the sun is near its highest, though the solstice is when the alignment is at its best.


One of the highest placed gnomons in the world, the spectacle it produces is considered one of the most impressive (you can find smaller versions in San Petronio in Bologna and Santa Maria degli Angeli e dei Martiri in Rome).

It's even more so when you consider that it was built more than 500 years ago. The Florentine mathematician Paolo Toscanelli is thought to have first placed the gnomon in the Duomo in 1475, while the Sicilian astronomer and Jesuit Leonardo Ximenes laid the meridian you see today in 1756.

It was designed partly so that “the measure of the year and the date of Easter be more accurately determined”, according to the inscription still visible on the wall near the choir: a valuable tool in the days when the most accurate way of measuring time was by observing the sun. 

Photo: Sailko, CC BY-SA 3.0, Wikimedia

Pre-telescopes, early astronomers also used it to study rarer events like sunspots, eclipses or the passage of Venus between sun and earth. Ximenes took careful measurements over several years to determine whether earth's axis of rotation was shifting, from which he concluded (correctly) that it was.

Today the gnomon no longer serves a scientific purpose, but remains a fascinating sight. The disc of light travels at around 7 centimetres per second across the glorious backdrop of the cathedral for roughly 30 minutes around 1 pm (which during summer daylight saving time is when “true”, solar noon falls).

Every year the cathedral invites guests to watch, with commentary from a guide, on several dates when the spectacle is at its best: in 2019, that will be June 11th, 14th, 18th and of course, the 21st.

You'll need to reserve by email ahead of time and arrive early to get a good seat. On the 18th, the commentary will be in English and in every case, entry is free. Find full details on the cathedral's website

If you can't make it in person – or if you just can't wait – here's a video of the show. 

This is an updated version of an article first published in June 2018.

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TRAVEL: How to visit Rome’s Vatican Museums

Planning a visit to the Vatican Museums? Here’s the most essential informaton you’ll need about tickets, when to go, what to wear and how to get there.

TRAVEL: How to visit Rome's Vatican Museums

As many people plan to visit their favourite sites in Italy this year after a long absence, we’re putting together our own quick guides to some of the country’s most-loved attractions. If you or someone you know is planning a trip to the Vatican Museums, here’s what to know before you go.


Advance booking isn’t required to enter the Vatican Museums, but it will help you avoid long queues at the entrance (those with ‘Skip the Line’ tickets still have to queue, but for less time).

If you’ve left it too late to book tickets for your dates in Rome, you should still be able to get in by turning up on the day – you just need to plan to spend an hour or so in line.

READ ALSO: Nine tips for making the most of a Rome city break

It’s safest to arrive early in the day to avoid disappointment; make sure to check you’ve found the right queue before committing.

Opening hours

The Vatican Museums are open 9am-6pm Monday-Saturday, with final admission at 4pm.

On Fridays and Saturdays from April 14th to October 28th, opening hours are extended to 10.30pm, with final admission at 8.30pm.

The museums are closed every Sunday apart from the last one of the month, when entry is free of charge; expect to contend with large crowds if you want to take advantage of this.

There are a few dates, including Christmas and New Years Eve, when the museums are always closed; you can find a complete list here.

Entry fees

Tickets cost €17 full price or €8 for children between the ages of 6 and 18, or students up to the age of 25. Children under the age of six are free.

A whopping €5 per person booking fee applies for all Skip the Line tickets, including discounted ones – so if you’re a larger group you may decide you’d rather just wait in line.

Entry to St. Peter’s Basilica is free, but be prepared to spend a long time queuing and go through an airport security-style bag check before you can enter.

(Photo by Andreas SOLARO / AFP)

When to go

The museums tend to be busiest on weekends, and on Mondays when many of Rome’s other museums and archeological sites are closed.

Most Wednesday mornings, there’s also Papal Audience at the Vatican’s Nervi Hall or in St. Peter’s square, which draws large crowds to Vatican City.

That means Tuesdays and Thursdays are often recommended as the best times to visit to avoid hordes of people – but as a world-famous attraction, there’s rarely a ‘quiet’ time to see the museums.

Dress code

As the Catholic state, Vatican City has its own, semi-strict dress code.

Shorts or short dresses or skirts above the knee are not permitted, and if your shoulders are exposed, bring a shawl or scarf to cover them. 

Hats aren’t allowed, and neither are exposed tattoos or messages that could be considered offensive to “Catholic morality, the Catholic religion and common decency”.

A free cloakroom service is provided for storing clothing and objects that aren’t allowed into the museums.


Getting there

Conveniently, there are a couple of A-line metro stops – Ottaviano and Cipro – right near St. Peter’s Basilica, and a number of buses also pass by or near the museums.

Rome’s centre is relatively small and walkable for a major European capital, and if you’re near the centre, you may find it easiest to go on foot.

If you’re on the River Tiber’s walking and cycle path, head in the direction of Castel Sant’Angelo and climb the steps when you arrive; Vatican City is just a short distance away.

How much time to budget

While many visitors are most interested in the Sistine Chapel, your ticket includes all of the Vatican Museums, and you’ll want to make sure you get your money’s worth.

The Vatican Museums are vast and contain a wealth of cultural and artistic heritage, from classical and Renaissance statues and busts to tapestries designed by Raphael, Michelangelo’s Pietà, a gallery of 500-year-old maps, and many more treasures.

You could easily spend the best part of a day wandering the museums, but if you’re in a rush, you’ll still  want to budget a good two-and-a-half to three hours.