The ancient Mayan tools of human sacrifice and bloodletting are shockingly exquisite: razor-sharp blades of shiny black obsidian, finely chiseled flint scythes and carved manta ray stingers.

In the most comprehensive collection of artifacts ever assembled from the Mayan empire for a single exhibition, it is the softly lit, artistic chamber of horrors tucked in a far corner that attracts the biggest crowds and the greatest curiosity. Perhaps it is because the pieces are, at once, instruments of almost unimaginable cruelty, elegant works of art and symbols of centuries-old unsolved mysteries.

But few in the crowd can avoid a shudder when reading the gruesome description of a 1,300-year-old obsidian dagger unearthed on Mexico's Yucatan Peninsula: "The big knives, delicately carved on each face, were used for decapitation in human sacrifices, or later, to rip out the heart."

The ceremonial utensils are part of the first major exhibit of Mayan artifacts to be collected from the entire region the Maya once ruled. That realm covered land that now constitutes part of Mexico and all of Guatemala, Belize, Honduras and Nicaragua--nations that usually hoard their patrimonial antiquities with the protectiveness of ancient Mayan governors.

The 557-piece display, called "The Mayas," took two years of international negotiations and $6 million to bring together, and was first shown in Venice before opening last month at Mexico City's Antiguo Colegio de San Ildefonso museum, where it will remain until Dec. 31.

The exhibit's organizers say they hope the exhibition will boost the current surge of public interest in Mayan civilization fueled by important recent discoveries at major ruins, an aggressive publicity campaign that has lured increasing numbers of tourists to Mayan sites in Mexico and Central America, and, inevitably, by the approach of the next millennium.

"The end of the millennium has renewed the public's interest in the spiritual vision of the Mayas and how all these ancient civilizations used to see the world and understand it," said Dolores Beistegui, director of the San Ildefonso museum in Mexico City's central historic district.

The works range from the macabre to the whimsical, from depictions of powerful gods to the daily activities of servant girls, from massive carved stone pillars weighing four tons to a spectacular royal death mask composed of 215 flawlessly linked pieces of jade. There are stone jaguars, ceramic crocodiles and seashell buzzards; figurines of fierce warriors, lithe acrobats and muscular athletes; and vases and urns for every occasion, be it carrying sacrificial blood, eating dinner or burying a loved one.

Of course, much of the allure of the Mayan civilization for modern-day tourists and archaeologists alike is that most of the culture remains veiled in mystery despite glyph-cracking computers, high-tech exploration aids and more scientists, academics and anthropologists than ever combing through ruins and poring over artifacts.

In fact, the descriptions of many items in the Maya exhibition often say more about what is unknown than what is known about an object or the creature it depicts.

Take "The Queen of Uxmal," an 8th-century (or so) stone carving of a finely detailed face emerging from the mouth of a snake. Well, it's not really a queen or even a female, for that matter. The experts note that it could have been the governor of Uxmal, a grand Yucatan Peninsula city, or perhaps it's the face of a young corn god. Take your pick.

To further clarify, the exhibit's catalogue offers: "If we consider that the serpent was associated with the land, it's not difficult to think that, like the corn plant shoots from the earth, the head of a deity emerges from the open jaws of the serpent."

Or note the extraordinary clay figurine of a bald bust nestled inside a fragile blue calla lily found on Jaina Island, off the coast of the present-day southern Mexican state of Campeche. It could symbolize "a person of advanced age or one recently born." And though similar figures often represent "real people," this work of art also could represent Mayan gods believed to be born from flowers.

But the attraction of ancient mysteries aside, "The Mayas" is above all an art exhibit, featuring some of the best Mayan artifacts culled from 40 museums in Mexico, Guatemala, Honduras, El Salvador, Belize and Costa Rica, along with a few recently excavated artifacts never before displayed in any museum. The show's coordinators estimate that it would take a dedicated museum-goer at least three months of nation-hopping to see the pieces of this collection in their home museums.

"The importance of this exposition is being able to see together these jewels of Mayan art that have been selected fundamentally for their artistic beauty," said Mercedes de la Garza, curator of Mexico's National Museum of Anthropology and a leading Maya scholar.

The exhibition has not been without its controversies, however. Several major European museums that lent pieces to the show at Venice's Palazzo Grassi refused to allow the works to travel to the Mexican exhibit because the artifacts originally were taken illegally or stolen from Mexico. European curators believed it would be possible for the Mexican government to refuse to allow those works to leave Mexico again.

"It's a very touchy point," said museum director Beistegui. "Bringing them here would seem to be asking for trouble."

Though it is now illegal for Mayan artifacts to be taken out of their countries of origin, archaeological theft remains a major problem in Mexico and Central America. Earlier this year, Mexican authorities recovered 39 pre-Hispanic ceramics being hawked at a roadside stand in the central state of Hidalgo. The works were believed to have been stolen from the giant Teotihuacan pyramids on the outskirts of Mexico City, one of the most heavily guarded and most visited of the country's historical sites. Last year U.S. Customs officials found 14 artifacts--some estimated to be at least 2,000 years old--in a shipment bound from Mexico to a New York art dealer.

"The Mayas" includes some stolen works that have since been recovered by the government. A stone column depicting a chubby-cheeked man in a feathered costume from the Late Classic period was "cut in slices like salami" by thieves who removed it from the Oxkintok site on the Yucatan Peninsula, according to Beistegui.

Though the carving, believed to be about 1,300 years old, has been carefully cemented back together, it bears the telltale scars of the powerful saws used to extract it from the ancient city.

Mexican authorities concede they have neither the money nor the manpower to protect or explore all the ancient sites scattered around the country. The National Institute of Anthropology and History has catalogued 28,000 locations--just over 10 percent of the 200,000 sites archaeologists believe exist in Mexico, according to Daniel Ortega, the agency's director of plans and evaluation. He said 172 of the historical sites are open to the public.

Mexico and its Central American neighbors have launched aggressive advertising campaigns in recent years to attract tourists and dollars to the cities of ancient civilizations that mysteriously began to be abandoned from about A.D. 1200 until the time of the Spanish conquest, and left to be reclaimed by jungles and other natural elements. Last year 2.8 million foreign tourists spent almost $2 billion visiting Mexico's "Mundo Maya," or Maya world, according to the tourism ministry.

The quest for tourist dollars, coupled with a newfound interest in keeping antiquities closer to their home temples, has fostered a revamping of Mexico's museum system. Until recently, most important relics were shipped off to the world-renowned National Museum of Anthropology in the nation's capital. Now local authorities have joined the political and financial movement to decentralize the Mexican government and have begun building museums adjacent to ancient city sites and demanding that the best artifacts be housed there.

But perhaps the most controversial issue of all, to some Mexicans, is the belief that their Mayan heritage is confined to museums and amounts to little more than relics of a lost civilization. In the anteroom leading into the exhibit "The Mayas" is a montage of photographs of living Maya from throughout Mexico and Central America.

"The Mayas aren't dead; they are still living," said museum director Beistegui. "We wanted to make a statement that there are still a lot of Maya in Mexico."

But in stark contrast to the excess of riches and power of the ancient Mayan civilization on display in the San Ildefonso museum, the Maya and other indigenous peoples of Mexico and Central America are the poorest populations in the region, long neglected by their governments. It was largely the demand for greater rights for indigenous people that led to the short-lived armed uprising of Zapatista rebels in the southern Mexican state of Chiapas more than five years ago.

"There is a strong disconnect," conceded de la Garza, who has spent 29 years studying the Maya, including rituals in contemporary Mayan society that are similar to those of the past civilization. "There is an absolute disparity between one and the other.

"The old Mayas were a great civilization that created this marvelous city and these marvelous works of art," she continued. "Then the Spanish conquistadors destroyed the Maya culture. They were totally stripped of their own territory and their culture, and they became the slaves of the Spanish."

Although Beistegui said she is disappointed that the Mexican government has not made a stronger effort to arrange more tours of the show for indigenous groups, she said, "We think this exhibit is very important to open people's eyes, to invite the public to discover a little more of its past. We want to make people realize how strong this civilization was and, after all these centuries, how it still survives."

CAPTION: Stone incense burners, including an effigy of the corn god, below, are among the artifacts on display in Mexico City from the region once ruled by the Mayas.

CAPTION: The circa 8th-century "Queen of Uxmal" emerges from the mouth of a snake.

CAPTION: Left, a Guatemalan stone carving of a governor chatting with a man in the image of a god; above, a Mexican figure on which sacrifices were placed.