Newlyweds took advantage last month of the beauty of the palace of Abd al-Rahman III among the ruins of Medina Azahara, in southern Spain. The city was built in the 10th century and sacked around 1010 by Islamic purists from North Africa.

The main gate of Medina Azahara. Houses are being built on the site of the Islamic metropolis, 90 percent of which remains unexcavated.

MEDINA AZAHARA, Spain - To hear historians tell it, this buried city three miles west of Córdoba was the Versailles of the Middle Ages, a collection of estates and palaces teeming with treasures that dazzled the most jaded traveler or world-weary aristocrat.

Pools of mercury could be shaken to spray beams of reflected sunlight across marble walls and ceilings of gold, according to contemporary records.

Doors carved of ivory and ebony led to sprawling gardens full of exotic animals and sculptures made of amber and pearls.

"Travelers from distant lands, men of all ranks and professions in life, following various religions, princes, ambassadors, merchants, pilgrims, theologians, and poets all agreed that they had never seen in the course of their travels anything that could be compared to it," wrote the 19th-century historian Stanley Lane-Poole in his book "The Story of the Moors in Spain."

Archaeologists are more hesitant, saying that while many of those marvels may have existed, physical evidence of them has yet to be found. But they, too, are full of superlatives.

"This was the largest city ever built from scratch in Western Europe," covering nearly 280 acres, Antonio Vallejo, the chief archaeologist here, said in an interview. "Most large Western cities grow over time. This was built in a single effort, from a single design."

Medina Azahara, also known as Madinat al-Zahra, was an Islamic metropolis built in the 10th century as a testament to Spain's proclamation in 929 that it was the true caliphate of the Muslim world.

The construction of the city, which began around 940, was a singular moment in history, when the most vibrant intellectual and cultural force in Europe was rooted in Islam, and when the heart of Islam was in many ways rooted in Europe.

But around 1010, Medina Azahara was sacked by Islamic purists from North Africa who considered the Muslim culture it represented far too liberal in its interpretation of the Koran. The raid effectively wiped the city off the map for a millennium.

Now, less than a hundred years after its ruins were identified and its location resurrected on modern maps, a new threat has emerged. Construction companies are putting up houses on the site of the city, 90 percent of which remains unexcavated.

Mr. Vallejo said he had faced many obstacles in the 20 years he has studied and worked to preserve the site - from inadequate funding to erosion. "But the biggest problem we have had is the building of these illegal homes," he said.

The local government in Córdoba, he said, has failed to enforce a law passed 10 years ago that expanded protections for the site against development.

A spokesman for the government, who observed Spanish protocol by requesting anonymity to avoid upstaging his superiors, said that the construction had practically stopped, and that in any event most of the houses were on the fringes of the site.

But Mr. Vallejo said that some 250 houses were on protected territory and that the government had not taken a firm stand against future construction.

The historical value of the site is difficult to overstate, he and other scholars say.

Medina Azahara represented a society that, despite its location on a predominantly Christian continent, became in many ways the embodiment of the Islamic world at its peak, when Muslim achievements in fields like science, philosophy and mathematics towered above virtually all others.

That society was called Al Andalus, the Arabic name for the Iberian Peninsula when it was under Muslim control, a period that lasted nearly 800 years, ending in 1492 with the surrender of the last Muslim stronghold in Granada.

María Rosa Menocal, a professor of Spanish at Yale and author of "Ornament of the World," a book about Muslim Spain, said that Al Andalus and its capital, Córdoba, were probably justified in considering themselves the center of the known universe when Medina Azahara was built. "There was no comparison between Córdoba and anything else in Europe in the 10th century - like New York versus well, a rural village in Mexico," she said in an e-mail interview.