Discover Pantheon

The Pantheon is, in the reference work's words, perhaps the most famous and architecturally most influential rotunda — and one of the best-preserved of all Ancient Roman buildings, in large part because it has been in continuous use throughout its history. Turismo Roma quotes Stendhal: the most beautiful remnant of Roman antiquity, a temple that has suffered so little that it appears to us as the Romans must have seen it in their own day.

It is two buildings with one inscription. Turismo Roma dates the first to 27 BC, when Marcus Vipsanius Agrippa — Augustus's son-in-law, friend and collaborator — built a temple here dedicated to all the gods. After the original burnt down, the present building was raised by Hadrian, who enlarged it, reversed its orientation and opened a porticoed square in front. The two sources date him differently: Turismo Roma says between 118 and 125 AD, the reference work probably dedicated about AD 126 — and explains why nobody is sure: Hadrian chose to re-inscribe the new temple with Agrippa's original inscription from the older one. The letters on the frieze still name Agrippa. Turismo Roma calls them the original inscription; the reference work calls them Hadrian's re-use.

Its proportions are a single number. The height of the building equals the diameter of the dome — a little more than 43 metres either way. Inside, five orders of 28 coffers narrow towards an oculus 8.92 metres across, and the dome remains, almost two thousand years on, the world's largest unreinforced concrete dome.

A gift saved it. Abandoned and then sacked, the building was given in 609 by the Byzantine emperor Phocas to Pope Boniface IV, who consecrated it as Santa Maria ad Martyres — preserving it from the spoliation that took many other ancient monuments. The Chapter dates the consecration precisely: 13 May 609, and the church has been used uninterruptedly ever since.

Rome's own bronze was not so lucky. In 1625, under Urban VIII Barberini, the portico was stripped of its bronze to cast the baldachin of Saint Peter's and 80 cannons for Castel Sant'Angelo — which produced the line the talking statue of Pasquino is credited with: Quod non fecerunt barbari, fecerunt Barberini. Two bell towers added at the same period, nicknamed donkey's ears, were taken down at the Unification.

Since 1870 it has been the sacrarium of the kings of Italy, holding Vittorio Emanuele II, Umberto I and Margherita di Savoia, along with artists including Raffaello Sanzio.

Admission is ticketed and it is not free. Turismo Roma gives the hours as every day 09.00–19.00, last entry 18.30, closed 1 January and 25 December, and sends ticket purchase to the Ministry's portal — but publishes no price, and no reachable authority does. What is free is stated by the Chapter: access to the liturgy is always free, and during it no tourist visit of any kind is permitted. It stands between Piazza Navona and the Trevi Fountain.

A temple front glued to a drum, and the join is the whole invention. The reference work records the building as round in plan except for the portico, with large granite Corinthian columns — eight in the first rank and two groups of four behind — under a pediment, and a rectangular vestibule linking the porch to the rotunda. That combination, a large circular domed cella with a conventional temple portico front, was unique in Roman architecture, and then became a standard exemplar when classical styles were revived.

The proportion is one number used twice. The height to the oculus and the diameter of the interior circle are the same, 43 metres. Turismo Roma puts it as the height of the building equal to the diameter of the dome, a little more than 43 metres, reflecting the classical canons of Roman rational architecture. A sphere of that diameter would touch the floor and the oculus.

The dome is still the record. Cast from Roman concrete, opus caementicium, it remains the world's largest unreinforced concrete dome almost two thousand years on. Turismo Roma makes the comparison differently, calling it larger than the dome of Saint Peter's Basilica — the reference work's bounded claim is the one that can be checked.

The weight goes into eight piers. Turismo Roma records the circular cella as girded by thick masonry walls and by eight great piers over which the dome's weight is distributed.

The coffering is structural and numerical. Five orders of 28 coffers narrow towards the top — lightening the shell as it rises — and 28 is a number considered perfect because it is the sum of 1 through 7. At the centre the oculus is 8.92 metres across and is the building's only light.

And the floor is a drain. Largely original, laid in porphyry, giallo antico, granite and pavonazzetto, it carries 22 almost invisible holes that take the rain the oculus lets in.

It was built twice, and the second builder signed the first one's name. Agrippa's temple of 27 BC burnt down; Hadrian raised the present building, enlarging it, reversing its orientation and adding a porticoed square in front. The reference work is explicit that the date of construction is uncertain because Hadrian chose to re-inscribe the new temple with Agrippa's original date inscription from the older temple — which is why Turismo Roma's 118 to 125 and the reference work's probably dedicated c. AD 126 can both stand.

The dome is cast, not built. It is Roman concrete — opus caementicium — poured as a single shell rather than assembled from blocks, which is why it has no joints to fail and why it is still the world's largest unreinforced concrete dome.

The load is managed by subtraction. Five orders of 28 coffers remove material from the shell where it is least needed, thinning the dome as it rises; the remaining weight is carried down through eight great piers within thick masonry walls. The 8.92-metre oculus removes the heaviest point of all — the crown — and lights the building at the same time.

Rain was designed for, not tolerated. The floor, in good part original, has 22 almost invisible holes cut through it.

And the reason it is still standing is social rather than technical. It is one of the best-preserved of all Ancient Roman buildings, in large part because it has been in continuous use throughout its history — use secured when Phocas handed it to a pope in 609.

Is the Pantheon free? No — not any more. Admission is ticketed. Older guidance, including an earlier version of this page, said it was free; that is out of date.

How much is it? No reachable authority publishes the price. Turismo Roma gives hours and an online purchase link but no figure, the Chapter does not sell tickets, and the Ministry's portal shows no price in its pages. Buy through the portal or at the door.

Is anything free? Yes. The Chapter states that access to liturgical functions always remains free and without charge — and that during them no tourist visit of any kind is permitted.

When is Mass? 17.00 Saturdays and days before feasts; 10.30 Sundays and feast days.

What are the opening hours? Every day 09.00–19.00, last entry 18.30, closed 1 January and 25 December. Hours may vary because of religious celebrations.

How big is the dome? The height to the oculus and the interior diameter are the same, 43 metres, and it is still the world's largest unreinforced concrete dome.

Who built it? Agrippa built a temple here in 27 BC; after it burnt down Hadrian built the present one — 118 to 125 per Turismo Roma, probably dedicated c. AD 126 per the reference work.

Why does the inscription say Agrippa then? Because Hadrian chose to re-inscribe the new temple with Agrippa's original inscription from the older temple — which is exactly why the construction date is uncertain.

Why is it so well preserved? In large part because it has been in continuous use throughout its history, secured when Phocas gave it to Pope Boniface IV in 609.

How long should I allow? Thirty minutes.