ALTOMUENSTER, Germany (AP) -- It was filthy, cramped and in major disarray, but when art historian Eva Lindqvist Sandgren entered the library in Altomuenster Abbey, off-limits to all but the German monastery’s nuns for more than five centuries, she immediately knew she was looking at a major treasure.

The dusty shelves held at least 500 books, by her estimate, including precious illuminated manuscripts from the 16th century, chants used by the uniquely women-led Bridgettine Order and processionals bursting with colorful religious and ornamental decoration in their margins.

Unlike most Bridgettine libraries, the tomes had survived the Protestant Reformation, the 30 Years War and Germany’s “secularization,” when the state took most church property. It represents the most complete collection of the order known today.

“I had entered a time capsule,” said Lindqvist Sandgren, a senior lecturer at Sweden’s Uppsala University.

Surprised by the spontaneous decision by Altomuenster’s last remaining nun, Sister Apollonia Buchinger, to open the library, 20 scholars including Sandgren made plans to return and meticulously catalog the remarkable collection. But before they could, the Vatican ordered the abbey in the Bavarian town of 7,500 closed and locked up the library, which also contains some 2,300 statues, paintings and other works of art.

If plans go ahead to close it down, all of the abbey’s property -- the books, the artworks, the city block-sized abbey and the acres of forests and fields that make up the monastery grounds -- would be turned over to the dioceses of Munich and Freising.

Altomuenster is the end of a subway line from Munich, one of Germany’s most expensive cities, and its land alone is thought to be worth tens of millions of euros -- assets that Sister Apollonia thinks the dioceses are eager to get their hands on.

Since 1496, the former Benedictine abbey in Altomuenster has housed a female religious order founded by Saint Bridget in Sweden in the 14th century. It is one of three monasteries of the original branch of the scholarly, monastic order operating today. But with its numbers in decline, Sister Apollonia now lives there alone. The Vatican requires at least three nuns to train novices to become nuns, prompting the decision to shut the abbey down.

The Franciscan nun the Vatican put in charge of the abbey’s closure, Sister Gabriele Konrad, said the library’s collection is just being kept safe but she has refused to grant the scholars or anyone else access to the books.

“The value of the library is the ensemble, because it’s never been taken apart,” said Corine Schlief, an art historian at Arizona State University who visited the library with Sandgren. “If this should be taken apart and divided up between books that collectors would give tens or hundreds of thousands of dollars for and those only of interest to scholars, it would lose a lot of its value.”

Schlief, Sandgren and other academics have written an open letter to the Vatican, Sister Gabriele and the Munich dioceses urging that the library be kept together and made available to the public and offering to catalog it.

Sister Gabriele and the Munich dioceses insist there is no plan to sell the books, and that their experts are perfectly qualified to handle them. Munich-Freising Vicar General Monsignor. Peter Beer dismissed speculation of any land-and-treasures grab by the dioceses.

“There’s a false impression that we’re taking in riches and gems and gold and everything imaginable -- that’s nonsense,” he told the AP at his office in Munich. “We are taking on costs more than anything.”

His office also downplayed the library’s potential value or historical significance, telling the AP it includes “a large number of antiphonaries from the 18th century, most in very used and some in damaged condition,” and that six antiphonaries -- books containing religious chants -- from the Middle Ages have “already been studied by scholars.”

That has made the group of scholars who wrote the open letter and others even more suspicious. From the hundreds of photographs they took, they know there’s much more -- including an illuminated manuscript from the 1500s in Belgium, which might be expected to fetch $105,000 or more if sold to a private collector, said Schier.

Volker Schier, another expert from Arizona State University, noted that even financially insignificant books are historically important. Ledgers, cookbooks and even antiphonaries help tell how the nuns lived over the centuries.

“Altomuenster is the holy grail,” he said.

Beer bristled at the offer of help from the group of scholars.

“You can be assured that we do not need any help from the USA to understand how to treat cultural assets of significance for Europe. We have a slightly longer history and slightly longer experience,” Beer said.

The dioceses plan to digitize all books dating from before 1803 and make them available online for researchers -- but Schlief says that is not enough.

“Digitization is laudable, but it never replaces the books themselves, which now need to be carefully studied and catalogued,” she said.

For her part, Sister Apollonia said if the Vatican decides to give her more time in the monastery, she would be more than happy to open the library to the scholars again.

“They need to be made available to the public,” Sister Apollonia said. “Maybe we could charge a fee and it could be a source of income.”