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(CNN) — Walk round Ascoli Piceno, and in some ways it could be any Italian town. There are two big squares where locals watch the days go by, sit in cafes to people-watch, and do their nightly passeggiata stroll. There are centuries-old churches and even ancient remains dating back to the Roman period.
As in plenty of other Italian towns, the center was constructed in the medieval period. And, just like others, it's been beautifully preserved.
But wander round -- especially at night -- and you'll notice one major difference: Ascoli appears to glow.
By day, the buildings and even the paving stones glimmer in the sunlight. And at night they glow in the moonlight, the towers, porticoes and streetlights reflecting perfectly in the flooring, making the city center look like a mirage.
That's all down to the fact that Ascoli's local rock, from which the entire historic center is constructed, is travertine: a precious stone, similar to marble, that gleams bone white in the midday sun, flushes pink with the sunset, and glows under the evening streetlights.
Today, travertine -- and Italian travertine in particular -- is expensive. You'll find it used in bathrooms and as flooring, rather than being used to make entire houses.
But Ascoli's travertine buildings and paving stones were laid long before it became an ultra-precious material. Many of the grand buildings you see today date back to the Roman period.
A miniature ancient Rome
The hills around Ascoli have rich travertine deposits.
Anca Emanuela Teaca/Alamy Stock Photo
Or rather, they were upcycled from Roman buildings -- which is why you'll find churches balancing on the visible remains of Roman temples, and chunks of arches and capitols blended into medieval and renaissance palazzos.
The Romans weren't the first to settle here, says Lella Palumbi, a tour guide in Ascoli. The town originally belonged to the Piceni -- an ancient tribe whose territory stretched over much of the modern Marche region, from Pesaro in the north to Chieti, in modern Abruzzo. They founded the city a century before Rome was born.
The Piceni were great warriors, says Palumbi, and the Romans, becoming more powerful, quickly sought to become allies. But the Piceni's request for Roman citizenship sparked a year-long war, culminating in the capture of Ascoli. Once in, the Romans razed the city to the ground and decided to rebuild it from scratch.
"That's when the travertine Ascoli was born," says Palumbi.
A sedimentary form of limestone, travertine is formed when hot springs deposit calcium carbonate minerals. It's notoriously porous -- almost elastic -- thanks to external organisms like algae, moss, bacteria -- and, often, fossils.
The sixth-century baptistery is one of Italy's greatest Romanesque buildings.
The Romans had already used it for their most important buildings and monuments in Rome, using quarries in Tivoli near the city -- they even called the stone "lapis tiburtinus," or "stone from Tivoli," which was later corrupted into "travertino."
Having conquered Ascoli, the Romans noticed there were similar quarries a few miles away, off the ancient Via Salaria. They used that stone to construct a glittering new city, to demonstrate their power over even the most battle-worn foes.
It was, says Palumbi, a "miniature Rome." There were temples, a court, spa facilities and a capitol. One square, Piazza San Tommaso, is still slightly rounded today because it sits on the ancient amphitheater; just outside the city center are the remains of the Roman theater -- one of the few ancient buildings to survive the medieval "recycling" of the city.
2,000 years of upcycling
The Roman theater is one of the few ancient buildings that wasn't recycled.
AGF Srl/Alamy Stock Photo
Roman Ascoli lasted well past the days of the empire, but in the medieval period, the citizens decided to rebuild. Instead of using new stones, as might happen now, they upcycled the Roman buildings, using the travertine cut 1,000 years earlier to build a modern city. Today, the churches of San Venanzio and San Gregorio Magno sit on the site of Roman temples, incorporating their stones into the building -- the latter has even recycled the pagan foundations, its back wall, and has even built its façade around two original Corinthian columns.
"Everything is recycled -- we took apart the Roman monuments to construct the medieval city," says Palumbi, who also owns a bar, Ozio, located in a medieval building using Roman stone that was revamped in the Renaissance.
"They were trying to save time and energy, so instead of going to the mountains to extract the travertine, they took what was already there -- the city was essentially a quarry." Look closely at the many towers which made this a medieval Manhattan (Ascoli was sometimes called 'the city of 100 towers'), and you'll see plenty of carved Roman slabs, she says.
Today, a Roman bridge (in travertine) is one of the main routes into town.
The town saw more restyling in the Renaissance period -- still exclusively using travertine -- making Ascoli Piceno a gumbo of architectural heritage that has never changed.
"Ascoli is the only city in the world made entirely from travertine," says Stefano Papetti, director of the five museums in town in his role as Ascoli's scientific consultant of the town's collections.
"It's different from Italy's other art cities -- they're mainly built in brick and then 'dressed' with travertine or marble. But here, whether it's the Roman, medieval, Renaissance periods or later, all the buildings are made with solid blocks of travertine, extracted from the mountains around Ascoli."
A Wes Anderson-style shapeshifter
Simone de Beauvoir and Ernest Hemingway have visited Caffe Meletti.
Francesco Russo/Alamy Stock Photo
Today, Ascoli Piceno is home to the highest concentration of Romanesque churches in an Italian city center. Its sixth-century baptistery is said to be one of the best examples of its kind in the country.
Ascoli's Pinacoteca Civica art gallery has works by Titian, Guido Reni and Carlo Crivelli -- a 15th-century Venetian painter who worked in the Marche region and died in the city. And its most famous bar, Caffe Meletti, is straight out of a Wes Anderson film with its baby pink façade, mint green tables and lavish Art Nouveau interior. Everyone from Ernest Hemingway to Simone de Beauvoir has tried its anis liqueur.
The town is even famous for its food. "Olive ascolane" -- oversized, juicy olives stuffed with meat and deepfried -- are eaten all over Italy.
The local art gallery has three works by Renaissance master Carlo Crivelli.
Archivio Iconografico Comune di Ascoli Piceno
Yet few things can compete with Ascoli Piceno's travertine buildings.
Piazza Arringo, the cathedral square, is surrounded by stately Renaissance buildings -- including the 12th-century city hall, where the art gallery is housed. Old gents sit on the travertine benches outside, watching water spurt from the mouths of two bronze seahorses in the fountain opposite. The fountain itself, of course, is travertine.
To get into town, you walk or drive over a Roman bridge, built of travertine.
Meanwhile, Piazza del Popolo, the other main square, is surrounded by Renaissance buildings -- the area was overhauled in the early 1500s.
Travertine porticoes hide the medieval shops that were considered not harmonious enough for the Renaissance. One side of the square is taken up entirely by the church of San Francesco, said to be one of the finest Gothic buildings in Italy. On another lies the Palazzo dei Capitani, complete with tower -- a castle-like building, now used by the local authorities, which holds regular exhibitions and allows access to the Roman marketplace in the basement.
Paved entirely in travertine, this is the square which glows at night, when artfully placed street lights make it look like the porticoes are melting into the ground, the palazzos are hovering, and the whole place appears to be a shimmering mirage.
"It's gorgeous at night with the illumination," says Papetti -- who adds that, in fact, Ascoli shapeshifts every day.
"Travertine has this quality of changing color depending on the sun and weather," he says. "It can be very warm -- for instance, it can flush pink in the sun. In bad weather it goes grey."
The rock that saved the city
Travertine is soft when first cut, before it hardens to thick stone.
Travertine has another particular quality that lends to Ascoli's beauty. When first extracted, it's relatively soft, allowing it to be sculpted -- one of the reasons Ascoli's buildings have ornate carved portals and facades -- many Renaissance houses even have mottoes carved over the doorways.
Then, through a chemical process of oxidization, it hardens into rock so resistant that the buildings of Ascoli have weathered multiple earthquakes over the centuries.
Of course, Amatrice was closer to the epicenter both times -- it was also destroyed in 1703. The terrain is also different -- Ascoli's is more stable than other nearby areas. But, says Papetti, "the stone helps make the buildings more stable."
Palumbi agrees: "The Romans were aware of earthquakes, and built Ascoli to resist them. They had better engineers than today.
"We could still happily live in Roman houses if we hadn't pulled them down."
Although the 2016 quake did cause damage -- several churches are closed for structural repairs, and post-quake surveys revealed that other buildings needed anti-seismic work -- nothing was destroyed, as it was in other towns in the region.
Giuliano Giuliani makes travertine as pliable as paper.
Ignacio Coccia/Giuliano Giuliani
For centuries, Ascoli's travertine quarries -- found in three areas around the city -- have been a crucial part of the town's economy.
Builders in the medieval and Renaissance periods used the Roman quarries on the Via Salaria. But in the 20th century, quarries opened up in the hills around the city -- particularly on Colle San Marco, rearing up behind town on the border with Abruzzo. Around 15 quarries sprung up in the postwar period.
Giuliano Giuliani's father opened one in 1952. His family was so wrapped up in their quarry that he likes to say he was born in it.
"I played on the stones growing up," he says. "I live in a travertine house and walk across travertine every day."
The quarry closed in the late 1980s along with others in the area -- partly down to economic crisis, partly because of environmental laws. But Giuliani has kept it.
Today, he's a sculptor. And of course, he sculpts in travertine -- mostly blocks from his father's quarry that had been cut before its closure. Sometimes, he buys the stone from the quarries that still exist in Acquasanta, west of Ascoli. And he describes working with travertine as "a spiritual experience."
"For me, it's the most beautiful rock of all, because it's a stratification, a history of its own, a blackboard of time, from the springs that deposited the rock, to animals who passed over and left fossils. It's a stage, telling the story of thousands of years.
"Just as a tree has circles of its years, in travertine you can read the centuries, the weather patterns and floods."
At night, Piazza del Popolo shimmers in the street lights.
Papetti, who's a fan, says that Giuliani can make the stone "soft as a sheet of paper." That's all down to the stone's "elasticity," says the artist. "When I decided I needed to be an artist, I chose the stone I grew up with -- partly because it inspired me, but also for technical reasons, because it allows me to make very light sculptures," he says.
His works -- thin and translucent, with that almost impossible papery quality that Papetti mentions -- have been shown at the Venice Biennale, Milan's Design Week, and Italy's 2015 Expo. His clients range from Pink Floyd's Roger Waters to the Vatican, and yet the unassuming Giuliani's heroes are, he says, the "incredible" men who used to detach the enormous blocks of stone from the mountain.
The quarry, swaddled by chestnut trees and oaks standing 2,300 feet above the city, is his studio. He even has plans to open a "school of travertine" where people from all over the globe can learn to work the stone.
What would Ascoli Piceno be without its travertine? "Nothing," he says. "Travertine means everything."