RIYADH, Saudi Arabia — Much of the world knows Petra, the ancient ruin in modern-day Jordan that is celebrated in poetry as "the rose-red city, 'half as old as time,'" and which provided the climactic backdrop for "Indiana Jones and the Last Crusade."
But far fewer know Madain Saleh, a similarly spectacular treasure built by the same civilization, the Nabateans.
That's because it's in Saudi Arabia, where conservatives are deeply hostile to pagan, Jewish and Christian sites that predate the founding of Islam in the 7th century.
But now, in a quiet but notable change of course, the kingdom has opened up an archaeology boom by allowing Saudi and foreign archaeologists to explore cities and trade routes long lost in the desert.
The sensitivities run deep. Archaeologists are cautioned not to talk about pre-Islamic finds outside scholarly literature. Few ancient treasures are on display, and no Christian or Jewish relics. A 4th or 5th century church in eastern Saudi Arabia has been fenced off ever since its accidental discovery 20 years ago and its exact whereabouts kept secret.
In the eyes of conservatives, the land where Islam was founded and the Prophet Muhammad was born must remain purely Muslim. Saudi Arabia bans public displays of crosses and churches, and whenever non-Islamic artifacts are excavated, the news must be kept low-key lest hard-liners destroy the finds.
"They should be left in the ground," said Sheikh Mohammed al-Nujaimi, a well-known cleric, reflecting the views of many religious leaders. "Any ruins belonging to non-Muslims should not be touched. Leave them in place, the way they have been for thousands of years."
In an interview, he said Christians and Jews might claim discoveries of relics, and that Muslims would be angered if ancient symbols of other religions went on show. "How can crosses be displayed when Islam doesn't recognize that Christ was crucified?" said al-Nujaimi. "If we display them, it's as if we recognize the crucifixion."
In the past, Saudi authorities restricted foreign archaeologists to giving technical help to Saudi teams. Starting in 2000, they began a gradual process of easing up that culminated last year with American, European and Saudi teams launching significant excavations on sites that have long gone lightly explored, if at all.
At the same time, authorities are gradually trying to acquaint the Saudi public with the idea of exploring the past, in part to eventually develop tourism. After years of being closed off, 2,000-year-old Madain Saleh is Saudi Arabia's first UNESCO World Heritage Site and is open to tourists. State media now occasionally mention discoveries as well as the kingdom's little known antiquities museums.
"It's already a big change," said Christian Robin, a leading French archaeologist and a member of the College de France. He is working in the southwestern region of Najran, mentioned in the Bible by the name Raamah and once a center of Jewish and Christian kingdoms.
No Christian artifacts have been found in Najran, he said.
Spearheading the change is the royal family's Prince Sultan bin Salman, who was the first Saudi in space when he flew on the U.S. space shuttle Discovery in 1985. He is now secretary general of the governmental Saudi Commission for Tourism and Antiquities.
Dhaifallah Altalhi, head of the commission's research center at the governmental Saudi Commission for Tourism and Antiquities, said there are 4,000 recorded sites of different periods and types, and most of the excavations are on pre-Islamic sites.
"We treat all our sites equally," said Altalhi. "This is part of the history and culture of the country and must be protected and developed." He said archaeologists are free to explore and discuss their findings in academic venues.
Still, archaeologists are cautious. Several declined to comment to The Associated Press on their work in the kingdom.
The Arabian Peninsula is rich, nearly untouched territory for archaeologists. In pre-Islamic times it was dotted with small kingdoms and crisscrossed by caravan routes to the Mediterranean. Ancient Arab peoples — Nabateans, Lihyans, Thamud — interacted with Assyrians and Babylonians, Romans and Greeks.
Much about them is unknown.
Najran, discovered in the 1950s, was invaded nearly a century before Muhammad's birth by Dhu Nawas, a ruler of the Himyar kingdom in neighboring Yemen. A convert to Judaism, he massacred Christian tribes, leaving triumphant inscriptions carved on boulders.
At nearby Jurash, a previously untouched site in the mountains overlooking the Red Sea, a team led by David Graf of the University of Miami is uncovering a city that dates at least to 500 B.C. The dig could fill out knowledge of the incense routes running through the area and the interactions of the region's kingdoms over a 1,000-year span.
And a French-Saudi expedition is doing the most extensive excavation in decades at Madain Saleh. The city, also known as al-Hijr, features more than 130 tombs carved into mountainsides. Some 450 miles from Petra, it is thought to mark the southern extent of the Nabatean kingdom.
In a significant 2000 find, Altalhi unearthed a Latin dedication of a restored city wall at Madain Saleh which honored the second century Roman emperor Marcus Aurelius.
So far, there has been no known friction with conservatives over the new excavations, in part because they are in the early stages, are not much discussed in Saudi Arabia, and haven't produced any announcements of overtly Christian or Jewish finds.
But the call to keep the land purged of other religions runs deep among many Saudis. Even though Madain Saleh site is open for tourism, many Saudis refuse to visit on religious grounds because the Quran says God destroyed it for its sins.
Excavations sometimes meet opposition from local residents who fear their region will become known as "Christian" or "Jewish." And Islam being an iconoclastic religion, hard-liners have been known to raze even ancient Islamic sites to ensure that they do not become objects of veneration.
Saudi museums display few non-Islamic artifacts.
Riyadh's National Museum shows small pre-Islamic statues, a golden mask and a large model of a pagan temple. In some display cases, female figurines are listed, but not present — likely a nod to the kingdom's ban on depictions of the female form.
A tiny exhibition at the King Saud University in Riyadh displays small nude statues of Hercules and Apollo in bronze, a startling sight in a country where nakedness in art is highly taboo.
In 1986, picnickers accidentally discovered an ancient church in the eastern region of Jubeil. Pictures of the simple stone building show crosses in the door frame.
It is fenced off — for its protection, authorities say — and archaeologists are barred from examining it.
Faisal al-Zamil, a Saudi businessman and amateur archaeologist, says he has visited the church several times.
He recalls offering a Saudi newspaper an article about the site and being turned down by an editor.
"He was shocked," al-Zamil said. "He said he could not publish the piece."