Originally Published: 18 JAN 22 06:35 ET

Updated: 18 JAN 22 06:38 ET

Julia Buckley, CNN

(CNN) -- It's world-famous for the Roman ruins of Herculaneum and Pompeii, destroyed by the eruption of Vesuvius in 79 C.E., but the latest tourist attraction in Naples shows a very different side of the city.

Opening in June, the Ipogeo dei Cristallini -- Hypogeum of Cristallini Street -- is part of an ancient cemetery, located just outside the walls of Neapolis, as the city was called 2,300 years ago.

Not only is the cemetery more than 400 years older than the ruins of Pompeii and the other Roman towns along the Bay of Naples, but it isn't Roman at all. In fact, it was built by the ancient Greeks, who founded Naples in the eight century B.C.E., and kept it a fully Greek city, even when it came under Roman control centuries later.

It's a game-changing opening, according to archaeologists, that promises to change how we think of Naples, the Mediterranean in ancient times, and even Greek artistry. It also, those involved with the project believe, has the potential to protect Naples from a tourism boom that, if it continues, could bring overtourism to the city.

In the bowels of the city

Forty feet below the garden of a 19th-century palazzo, in what's now the Sanità area of the city, a steep staircase burrowing underground leads to four tombs. Each with their own grand entrance -- one even has Ionic columns sculpted on its façade -- they open on to what is thought to have been the original pathway that mourners would have taken.

This is only a small part of the original necropolis, or cemetery, built by the Greeks. In the fourth century B.C.E., when the tombs are thought to have been built, dozens of them would have been dug into the hills outside the city walls, says Luigi La Rocca, who, as Naples' Soprintendente, is in charge of the city's archaeological heritage.

Ancient Greeks built twin-chambered tombs -- one upper chamber, where prayers were said, and a lower one, where the bodies were laid to rest -- by digging out the soft tuff rock, rather like making a cave.

But these are no mere caves. The chambers have been sculpted to resemble real rooms, with fake ceiling beams, benches, staircases and even high-mattress "beds" -- sarcophagi, inside which multiple bodies were laid to rest. And these weren't sculpted outside and then brought in. Every single detail -- right down to the perfectly plumped "pillows" on those beds -- has been carved from the original rock face.

Precious paintings shed light on Greek art

Although they're now underground, their entrances would originally have been street level -- hence those imposing Ionic columns, signifying the elite status of its inhabitants. Only the lower chamber would have been subterranean.

But centuries of mudslides that regularly devastated the area -- only ending in the 1960s when the sewerage system was overhauled -- buried the tombs a few centuries after they were built.

That means their level of preservation is exceptional, according to archaeologists. Crucially, they still retain their vibrant wall paintings.

Ancient Greek art, of course, is known the world over -- but what has survived is for the most part sculpture.

"Greek painting is almost completely lost -- even in Greece there's almost nothing left of painting, though we know from sources that it was important," Federica Giacomini, who has spent the last year overseeing the monitoring of the site for Italy's ICR, the Central Institute for Conservation, told CNN.

"There's basically nothing left of anything painted on wood or furniture, and there's very little wall painting -- mainly Macedonian tombs that conserve important pictorial murals, but it's almost nothing.

"We have lots of Roman painting, but much less Greek. So this is a rarity, and very precious."

Down in the depths

The painted tombs give a very different impression of Greek art to those bone-white sculptures and buildings (which, too, would have originally been colored). One tomb has scarlet-painted steps leading down to a red faux-marble floor. The stone pillows -- turquoise with yellow stripes -- have red hatching on the side, imitating cross-stitch threading the textiles together.

Meanwhile the walls are lavishly frescoed: lush garlands swinging from columns, flaming candelabras, vases and dishes that were used in funerary rituals, and even two human figures, thought to be the god Dionysus with Ariadne, the woman he gifted with immortal life.

There's even a sculpted gorgon -- the mythological beast with a woman's head but snakes for hair, as they twist and curl around her pretty face. She's the only element of all four tombs to be sculpted and attached, rather than dug out from the hillside.

On the walls, meanwhile, are scrawled names in ancient Greek: lists of those buried inside.

The other three tombs are equally interesting, if not as spectacular. One was also frescoed, although the paintings have been damaged -- it's hoped that future restoration will bring them back to light.

In another lie six headstones, dedicated to the dead. Each lists the name of the deceased, and signs off with the inscription "khaire" -- an ancient Greek greeting, akin to the "ciao" that modern Neapolitans use.

The tombs even have niches carved by Romans, who reused them to bury their own dead after the original Greek dynasties had died. In all, the necropolis was in use from the late fourth century B.C.E. to the early first century C.E. before being buried by mudslides.

Elsewhere are sculptures of people, and traces of portraits -- potentially dead ancestors, according to Paolo Giulierini, director of the National Archaeology Museum of Naples, which houses hundreds of finds from the tombs, including sculptures, vases, and carved symbols of resurrection, such as pomegranates and eggs.

A city of the dead beneath the modern city

These aren't the only tombs of the ancient necropolis have been found. La Rocca says that around 20 have been identified under buildings in the Sanità district, which was built in the 16th century. Some of them conserve paintings, and archaeologist Carlo Leggieri leads visits to five of them -- including three partially frescoed tombs, and another with a remains of a sculpted panther. But, Giulierini says, these look to be the most important so far.

Damaged by building work in the 1700s, the tombs were officially discovered in 1899, but have always been closed to the public -- until now.

Archaeologists have been monitoring the environment since May 2021 to understand potential hazards. Once they complete a year's monitoring, the tombs should be opened for limited visits while restoration work commences. Visitors will be able to see the tombs as they are now -- largely as they were when discovered -- and be present as they are gradually brought back to life.

Those in the know have high hopes.

"It's a space of extraordinary importance because it furnishes us with precious data about the beliefs and the social structure of Neapolis in the Hellenistic and Roman eras," La Rocca told CNN.

Giacomini calls it "a testimony of a civilization that we have extremely few traces of."

For Giulierini, it's proof of the high status Neapolis ("new city" in Greek) once held in the ancient Mediterranean. The tombs best resemble those found in Macedonia -- the homeland of Alexander the Great, covering modern North Macedonia and northern Greece.

"This shows that Neapolis had a huge international profile," he told CNN, calling it a "top ranking cultural capital" along the lines of New York, London or Berlin today.

Changing Naples tourism

Giulierini -- who curates tens of thousands of objects from Pompeii and Herculaneum at his museum -- hopes that the tombs will also correct the "imbalance" in how visitors today perceive the city, linking it to the Roman ruins in the area.

In fact, he says, while the citizens of Pompeii were holding bloodthirsty gladiator games, the people of Neapolis were hosting a more refined take on the Greek Olympic Games, launched by the emperor Augustus. Another emperor, Nero, came to perform on the stage in Neapolis, before later touring Greece. And they had, of course, for centuries been burying their dead in grand painted chambers dug into the hillside.

Meanwhile, La Rocca hopes that the opening will help bring more cultural tourism to Naples, which is currently seeing a tourism boom.

"Naples is more than ancient but it's not often seen as an archaeological city," he said. "The city should be told through its archaeological remains, but these are mainly known by professionals. Sadly many monuments are not open to the public."

"Sustainable tourism in relation to cultural preservation," could be a way forward for the city, he added.

The Ipogeo dei Cristallini will open for limited visits in June. Carlo Leggieri's tours of the other tombs can be booked by email: carlo.celanapoli[at]gmail.com

Main image: Archivio dell'arte, Pedicini fotografi