Pantheon Inside and Out: Hidden Rooms Now Open

You know the Pantheon. It's the best preserved ancient Roman monument, the best temple from imperial times. And what you don't know is the Grottone. And these are structural rooms behind the rotunda that serve to shore up the backside of the rotunda wall. Now it's a site that you can visit every day. Let's go explore this new experience to understand I've already shown you these Grottone spaces in a previous video, but now we can visit the site on a daily basis with a new museum installation. You get a separate ticket and enter here in the back. You've stepped inside the Grottone spaces, the grottos as they became known, structural rooms constructed to support the rotunda on the south side of the Pantheon. Here we can view a space that's been converted into a chapel containing the 7th century icon that used to be on display inside the Pantheon when it was first converted into a church, Santa Maria ad Martires in 609. It's rarely on public display, but we can admire it here. We walk under some massive arches and then the area is narrow as we pass behind the bulge of the apse of the adjacent building, the Basilica of Neptune. We ascend the modern staircase or take the elevator into the larger upper rooms in which the museum has been installed. The walls and the vaulting are the impressive remains of the grottos, radial vaults buttressing up against the southern end of the Pantheon rotunda that had some structural failings during its construction. All right, with this new museum space, you've got examples of Christian Rome. You've got examples of medieval Rome. You've got examples of how they constructed it and its placement within the campus marshes. It's a great experience. It's didactic. It's accessible. It's extraordinary. And then where are we? We're in the actual physical spaces. Look at this. We're inside the Grottone on two floors. This is a masterful presentation of all this information. It's a place you need to come and visit. These views of Gismondi's famous Plastico of Rome show us the porch and the rotunda of the Pantheon, as well as the Grottone spaces and the adjacent Basilica of Neptune, a large hall that was probably part of the Basilica of Grippa. A neighborhood plan helped set the scene. This close-up plan clearly shows the Pantheon, porch, rotunda, and the Grottone spaces neatly wedged in right behind the rotunda, followed by the Basilica of Neptune Hall. The reconstruction drawing by Georges Jadin and his model helped put it in perspective, as does the model of the Pantheon that shows us what is preserved today of the Grottone and the small portion of the Basilica of Neptune, but it's been gobbled up by modern buildings. This was an enormous hall that was part of the bath complex of Grippa that's going to be rebuilt in the Hadronic period as you have the rebuilding of the Pantheon. So directly behind this building, with this apse, this apse is going to encroach upon the Grottone. To understand the Basilica of Neptune, let's now walk behind the Grottone spaces and into the remains of the Basilica of Neptune that directly abuts the Grottone Hall and look at the original ground level and we can admire the interior architectural features with some anastolosis of the column. Here we can see the dolphin and the trident features of the frieze that help us identify this as the Basilica of Neptune, originally built by a Grippa who won the sea battles of Naulicus in 36 BC and of Actium in 31 BC or Augustus. Inside the museum has a display of some of the original fragments of the entalmature that we can admire at eye level. There are also impressive videos that show imaginative reconstructions of the Basilica of Neptune with its once impressive vaulting as well as marble veneered walls. The statue base in the niche was once filled with a colossal statue of Neptune or maybe Hadrian. Truly this was a masterpiece in the Campus Martius that mirrored the decoration of the Pantheon itself. Other videos help us envision the Campus Martius, that floodplain of Rome that changes over time. Here we see images of the area before the construction of the Augustan Age buildings. We just see the Theater of Pompey and the Largo Argentina temples. We can really get a good sense of the Pantheon as it stands today from the porch to the rotunda and now this accurate view of the as well as the preserved remains of the Basilica of Neptune. The museum also displays these two nearly identical carved slabs that were originally placed in the porch or pernaus of the Pantheon. They were discovered in 1874. They had been reused as steps. Let's look at this important collection of brick stamps that date from the reign of Trajan to the reign of Hadrian. The Pantheon burned down in 110 so it is now certain that these manufacturer stamps underline that the reconstruction of the building started under Trajan, if not the design of his famous architect Apollodorus of Damascus. And the Pantheon was completed then in the reign of Hadrian. One of the most frequently appearing stamps is that of Capitanus Favor, Aquileus Aprillius, and Portilius Agustalis of the Trajanic-Hadrianic era. There are also brick stamps from the reigns of Domitian and the Severans that refer to the periods of restoration. In fact, the Domitianic Pantheon replaced Agrippus Pantheon that was then destroyed in 110. They've been replaced by the Pantheon we have up today. The oculus opening in the dome, allowing sunlight, created a sort of interior sundial. Although we are not sure about Agrippus' original Pantheon, the Trajanic-Hadrianic one displays all kinds of stunning experiences, in particular on the solstices and the equinoxes. The only problem with the displays today is that they refer to the sky of the 21st century and not that of the original sky when the Pantheon was designed in the 2nd century AD. So the light shows of today were not those of 1900 years ago. Stay tuned for some new scholarship on where the light would strike the interior spaces as originally intended. The Cretonia Museum space also displays some interesting artifacts from the Christian era, beginning with the impressive marble chiborium, the canopy-like structure over the altar, and it dates to 750 to 850. Here's an early 6th century marble screen slab. Here's a fresco fragment of the 12th to 13th centuries from the main chapel dedicated to Saint Thomas, later replaced by the tomb of King Umberto I. We have a 13th century decorative panel for a tomb or a wall. A portion of a fresco from the 14th century from the main chapel. Here's a tomb slab of Colla di Paolo, dating to 1410. A 15th century fragment by Innocent VIII of a presbyterial enclosure. A fascinating 17th century alms box reusing an ancient funerary altar. There are 17th century tombs. There's an inscription from Clemens XI of 1718. There's an original edicule that held the icon dating to 1711. And an 18th century tabernacle. There are 18th and 19th century busts of cardinals in the canon of Santa Maria at Martires. And the rooms also house a lot more from the church and from the Basilica of Neptune. It's amazing to consider such an impressive museum space originally used just for structural purposes now gives us a really good look at Roman engineering and architecture at the same time. This is quintessential high empire in its building and now it's time to exit. We need to go from the Grottone into this tight little space to go inside the Pantheon. One of the great, great experiences you get when you're in the back rooms. Unbelievable. Look where we are. From the Grottone into the Pantheon. What an experience. Thanks for joining me inside the Pantheon, behind the Pantheon, to those hidden unexplored spaces. You can follow me on YouTube, Instagram and X. It's always Darius Ariadigs. We'll see you somewhere ancient in Rome and throughout the Mediterranean.