EACH SPRING, Maharaja Gaj Singh II hosts a Sufi music festival inside his family's vast desert fort in the Indian city of Jodhpur. From a distance, this monumental sandstone fortress, called Mehrangarh, looms over the city's chalky blue buildings, evoking the country's ancient and otherworldly history. And yet people fly in from across the globe because the festival—and the maharaja who hosts it—blends old India so deftly with new.

On the festival's opening night this year, thousands of visitors filed into the fort's crenellated stone courtyard—once reserved for royal wives—to cheer on Rabbi Shergill, a Punjabi rocker whose black turban matches his electric guitar. Singh, age 65, sat in the front row and applauded the performance along with the rest of the audience, but afterward it was he who drew the longer line of well-wishers. Foreigners slapped Singh on the shoulder, shaking his hand. Locals, who know his history better, chose to genuflect, stooping to touch his shoes.

Photos: Your Majesty Click to view slideshow. Photography by Robert Polidori

Maharajas, or great kings, once controlled huge swaths of India, and for centuries they commissioned artworks and palaces to rival those of medieval and renaissance Europe. But like those bygone feudal lords, modern maharajas have slipped into relative obscurity—particularly after the democratic Indian government ceased to recognize their titles and cut their government subsidies, or privy purses, in 1971. A handful of maharajas are still keeping up appearances, but in reality few have successfully managed the transition into modernity. Even worse, conservators say, many of the historic sites the maharajas once oversaw are now falling into ruin or being renovated beyond recognition.

Several thousand people used to live within the walls of Farrukh Nagaur Fort, an 18th-century fortress that now sits in a booming industrial suburb of New Delhi; today, parts of Farrukh Nagar's walls are crumbling, its only residents a colony of bats. Over in Alwar, a hilltop city in Rajasthan, the government museum within the city palace is in even rougher shape: When Dubai-based art dealer Charlie Pocock walked through it a few years ago, he found ornate silk curtains fading in the sunlight and hallways reeking of urine.

"The mind-set in India is that when things get damaged, they lose value and ought to be demolished," says Tasneem Mehta, vice chairman of the Indian National Trust for Art and Cultural Heritage, or Intach, a nonprofit preservation group based in New Delhi. "There isn't a sense that we should maintain what's sacred. We tear down and build anew."

FAMILY AFFAIR | Gaj Singh II, known to some of his staff as the 'Jazz Age maharaja' for his love of jazz, in front of a portrait of his ancestor, Takhat Singh Photography by Robert Polidori

This disregard for India's historical treasures makes Singh's activist approach to preservation an anomaly. Born a year after India won its independence from Britain in 1947, he was only 4 years old when he was anointed his region's ceremonial ruler, after his father died in a plane crash. He was only 22 when the government cut off his subsidies. By his rights, Singh could have mimicked other maharajas by profiting from the sale of his birthright properties or letting them crumble to dust. Instead, he doubled down and launched a conservation program in 1972 that's since become a national model. He started humbly, by hiring workers to muck out the bat droppings piling up in Mehrangarh, which had been closed since his family moved out in the 1930s. Then he added an entrepreneurial twist by selling that guano to local farmers as fertilizer and adapting the fort into a museum. Since then, his projects have only grown in complexity and acclaim.

Today, his second fort in nearby Nagaur, called the Fort of the Hooded Cobra, is a time-warp marvel, a sprawling complex of 18th-century palaces, temples and pools that look cared for but not overly polished. The 12th-century wall encircling it all has been repaired with a traditional paste made from sand and sheep's hair. Its gardens are lush with plants Singh's conservators have identified in Mughal-era miniature paintings. In the Sheesh Mahal, or mirror palace, murals of girls dancing in the rain look cleaned, but not repainted—even though their original vegetable dye has faded. "When you grow up in a desert, monsoons are a magical thing," Singh says of the mural's theme. "There is so much history to remember and protect here."

In addition to Mehrangarh and Nagaur, Singh also oversees several other palaces, 5,000 paintings and a museum's worth of eclectic heirlooms, from his great-great grandfather's elephant-riding chaise to his grandmother's Rolls-Royce Phantom II. All of it has been inventoried and catalogued so curators can study or borrow pieces, an open-door attitude that's still rare among Indian collectors, says Debra Diamond, a curator of Southeast Asian art at the Smithsonian's Freer and Sackler Galleries. "Many Indian collectors won't let you in or won't let you photograph anything," she says, "but he understands how scholars work."

By all accounts, the gem of Singh's collection is Mehrangarh—the Citadel of the Sun—the ornate fortress that his ancestor Rao Jodha built in the 15th century on a hill 400 feet above his namesake city. A century ago, Rudyard Kipling called the fort "the work of angels, fairies and giants." Singh opened Mehrangarh to the public in 1973 (after the guano was gone); last year, a million people stopped by—about as many as visited the Solomon R. Guggenheim Museum in New York or the Rijksmuseum in Amsterdam.

Not unlike Britain's land-rich-cash-poor aristocracy, Singh has had to find creative ways to fund the refurbishment of his properties. Accordingly, he turned a portion of the second fort in Nagaur and the 347-room Umaid Bhawan Palace in Jodhpur—both ancestral sites—into luxury hotels. He, his wife and children live in the southern wing of the Indo-Deco palace behind a door draped with an auspicious garland of ashoka leaves. The palace's general manager, Ashish Kumar Rai, says hotel guests regularly spot Singh having a drink in the Trophy Room bar or swimming in the pool. "His highness is a big draw, actually," says Rai.

Lately, word of Singh's endeavors has rippled beyond Rajasthan, making him a favorite in art and fashion circles. Museum directors from Washington, D.C. to Houston have made annual pilgrimages to Jodhpur to see what Singh's scholars have uncovered. Celebrities like Naomi Campbell and Elizabeth Hurley have been lured there by the fact that they can rent his forts' courtyards for an undisclosed event fee.

By first rescuing his properties and then catering smartly to the tourists that have followed, Singh is offering India a new way to think about its historic spaces, says Jim Cuno, president of the J. Paul Getty Trust, which has given grants to Singh's project in Nagaur. "The ancient world is everywhere you look in India, but it's being neglected in the name of modernization," says Cuno. Singh, on the other hand, is "reinvigorating India's older story."

Indian conservators say Singh's conscientious model is slowly starting to catch on. The country's expanding middle class is traveling more, and municipal governments are realizing they can attract more tourists by sprucing up their local attractions. But too often their efforts bog down midway through, says Anupam Sah, head of art conservation at Mumbai's main museum, the Chhatrapati Shivaji Maharaj Vastu Sangrahalaya. Sah recently started a national program called the Art Conservation Resurgence Project to stoke greater cooperation among conservators. "Official support for these sites is huge, but we can't always seem to implement what we want to do," says Sah. "Bapji is a case study in how to do it." Bapji, a Marwari word for "father," is the maharaja's nickname.

Singh's approach to preservation is more than a way to hang on to his ancestral footprint. It's also a way to preserve whatever power he still has as a maharaja. Eight years ago, he was devastated when his son and heir, Shivraj, nearly died after cracking his skull in a polo accident. Now 37 years old, Shivraj has regained his memory and relearned to walk, but speaking remains a struggle, and the ordeal has rattled the family's succession plans. By tradition, only Shivraj can take over the mantle of maharaja, unless he and his wife have a son.

In the meantime, Singh says he has started relying more heavily on his anthropologist daughter, Shivranjini, age 38. When she opened a gift shop in their palace a few years ago, she hung a red banner out front touting "The Most Beautiful Things in the Realm."

"Exactly what is my role now?" Singh asked one balmy night a few months ago, his low voice muffled by his bushy salt-and-pepper mustache. Standing on the ramparts of Mehrangarh, with traditional dancers twirling in a nearby courtyard, he let his question drift for a few moments. "There is no clear path, and anyone in my situation has had to figure it out in his own way. All this looks appealing, but it hasn't been easy."

FIT FOR A KING | The steps of Umaid Bhawan Palace, from which Mehrangarh is visible. Now partly a Taj hotel, revenues are up 80 percent thanks to a boost in domestic tourism. Photography by Robert Polidori

RAJASTHAN, THE REGION where Singh grew up, means "the abode of kings." It is comprised of several former fiefdoms like Jaipur, Jodhpur and Udaipur that have alternated as rivals and allies throughout history—all the while sharing a cultural penchant for art. In Jodhpur, a clan called the Rathores has held sway since 1226.

Singh is the Rathores's 38th successive ruler, yet he was born into a time of great flux. His grandfather, Umaid Singh, befriended the British and balked at Mahatma Gandhi's call for self-rule. Umaid's own attempts to modernize Jodhpur stalled when he died of appendicitis two months before India earned independence. Umaid's son, Hanwant Singh, was willing to try his hand at democratic politics, winning a 1952 election to become a regional minister. But on election day, en route to thank voters, Hanwant flew his plane into an electrical wire and died. He was only 29.

After his father died, Singh says he remembers being dressed up and placed, barefoot, upon a marble throne at Mehrangarh, surrounded by a horde of unfamiliar men in turbans. One of the chief clansmen pricked his own thumb on a sword and anointed Singh's forehead with blood. Singh was told he now had "more responsibilities."

He grew up in a mostly empty palace in Jodhpur with his grandmother, mother and his two older sisters. "It was gloomy," he says.

Worried about the absence of a father figure, Singh's mother sent him to the prestigious British school Cothill House at the age of 8. For weeks he wrote letters, begging to come home. He even deceptively hinted that the staff was making him eat beef, a Hindu taboo. Eventually, though, he discovered how to defend himself from his classmates' taunts. Yes, he told them, he did have lots of wives, and yes, he was allowed to hunt tigers. (Neither was true.) "They teased me, so I learned to tease right back."

Singh grew to admire aspects of Britain's culture, mainly its orderliness and the reverence its citizens paid to their history. He appreciated the way Europeans spoke about their ancient spaces, as if they were objects to protect as is, rather than overhaul like other kinds of real estate—a realization that reinforced his belief in the "importance of authenticity," he says. "I was impressed by the way old and new spaces worked side by side." Halfway through his later studies at Eton, he found himself wishing he could become an architect and work in Britain forever. The urge unnerved him. "I knew I had to go back," he says.

In 1970, after graduating from Oxford, he and a couple of friends drove across Europe and part of the Middle East, mainly to sightsee and study architectural landmarks. When they arrived in Tehran, Iran, a telegram from Singh's mother cut everything short. Political tensions were brewing at home and he was needed there—for good. One of his travel companions, David Campbell, says he was stunned by the reception Singh got when he stepped off the train platform in Jodhpur: "It took Bapji nine hours to get from the railway to the palace because the crowds were so excited—their maharaja was home." Singh was 22 years old.

At the time, his effusive homecoming stood at stark odds with the nation's shifting perception of maharajas. In a country where millions still live without electricity or running water, here were dozens of royal families in palaces being funded in part by taxpayer subsidies. Still, Singh resented being called a "millstone," he says. "The press thought all the maharajas were bad, and I felt deflated by it all." Complicating matters was the fact that the Marwari villagers who populated the desert surrounding Jodhpur didn't care who was officially running India—after all, they had a tribal chief tasked with making their lives better: Singh. Recalling an early visit to some desert towns outside Jodhpur, Campbell says he brought up the prime minister at the time, Indira Gandhi, in a conversation with a villager. The name drew a blank. "When something went wrong," he says, "they went to their king."

Months after Singh returned home, the government amended the Indian Constitution to abolish the maharajas' allowances, which had ranged from a few thousand dollars a year to $100,000 or more. Land reforms followed suit. Suddenly, Singh had to maintain his properties on a dime, or sell them off piece by piece. What he did instead was set up a nonprofit, the Mehrangarh Museum Trust, to which he commended the running of his main fort and the collections it contained. After a brief ambassadorial assignment in the West Indies in the late 1970s, Singh returned home determined to build his reputation on conservation causes, not political ones.

In 1984, he became a founding member of Intach, the nonprofit group in Delhi that has since become a national powerhouse for protecting ancient sites across the country. In earlier eras, maharajas had raised crops and taxed their subjects to cover expenses, but after Singh lost most of his lands and had to raise funds on his own, he leveraged whatever cultural assets he still had to gain attention. He invited conservators and curators to pore over Mehrangarh's collections—vast rooms filled with 1920s-era crates containing armor, painting scrolls and howdahs, chairs designed to sit atop elephants. Professionals in various fields—art conservation, archivism—cleaned and catalogued the priceless objects.

Mehrangarh became the first fort in the country to boast its own conservation lab, says its current director, Karni Jasol. So many scholars from India and abroad eventually signed up to do research on-site that the maharaja ordered some of the fort's upper rooms be converted into apartments so they could stay on for months, even years. On the financial side, admission fees to Mehrangarh began to cover its operational costs as tourist numbers steadily climbed.

With Mehrangarh in working order, Singh turned his attention to Ahhichatragarh, or the Fort of the Hooded Cobra—a group of elaborate palaces clustered behind a high moat wall in Nagaur, a former caravan stop 90 miles northeast of Jodhpur. In the 18th century, one of Singh's ancestors redesigned this 12th-century fort as a kind of watery pleasure palace, with complex interconnecting pools and fountains. During the 1970s, when political tensions with Pakistan flared up, Singh agreed to lease the fort to the border security force, but he later regretted the decision when he found out the soldiers posted there had nearly reduced it to rubble, plastering in arched windows and slathering mint-green paint over walls that are older than the Taj Mahal. After years of petitioning and lawsuits, Singh ultimately convinced the government to give up its lease in 1985.

What happened next largely explains why people are hailing Singh as a prototype for heritage management. Instead of plunging in with bulldozers and buckets of paint—the renovation norm at the time—Singh spent months hosting symposiums and conducting environmental assessments at Nagaur before he and conservation architect Minakshi Jain sent in a single worker to clean up. That academic approach appealed to the Getty Trust, which gave him a $50,000 grant in 1992 and followed it up later with $250,000 more.

Lady Helen Hamlyn, a London philanthropist whose trust matched the Getty's grant to aid the fountains, gardens and murals in Nagaur, puts Singh's contribution bluntly: "For a long time India couldn't see the point of saving ruins because it wanted something new," Hamlyn says. "Not Bapji, though."

Today, nearly all of Nagaur's 100 splendid fountains and pools are once again in working order. Visitors can stay in quarters once reserved for the 18th-century maharaja's many wives. Sibylla Tringham, a wall-paintings conservator at the Courtauld Institute of Art in London, who has spent years saving the fort's murals, says that peacocks, which once ran wild here, have even returned to the grounds. The feeling of renewal, from the murals to the wildlife, is hard to miss, says Tringham. "It's all telling a story."

For locals, that story is about the revival of Rajasthan's architectural wonders and the shifting mandates of the maharajas—but it's also about them. The assistant director of the fort at Nagaur, Abhimanyu Singh, is not related to the royal family, but he says their ties run deep in other ways. Growing up in the desert nearby, his relatives used to regale him with tales about how one of his ancestors had once worked for Maharaja Bakhat Singh, the ruler who originally made Nagaur a watery wonderland in the mid-1700s. "I've been hearing about this empire ever since I was a little boy," he says.

The endearing thing is, so has the maharaja. Gaj Singh says his own grandmother told him stories about the "heroics of my ancestors." Everything he's done, in fact, has been his subtle way of keeping up. "In India, we have so much freedom and desire to break away from the past," Singh says, "but I tell my children they have to stay connected. They have to find a link to both worlds."

Write to Kelly Crow at kelly.crow@wsj.com