Luxurious white marble lines the 104-foot-long oval, along with dark green serpentine tiles forming squares, diamonds, and a Greek key pattern. (You can actually see the tilework better now that the pool is dry.) Both types of stone have corroded over the years, so restoration architects Page & Turnbull are tracking down replacements at Vermont quarries. They’re also working to address persistent water leaks.

Seventeenth-century statues of Neptune and the Nereids overlook the pool, which once served as the centerpiece for lavish parties hosted by Hearst Castle’s famous residents, William Randolph Hearst and Marion Davies. Cary Grant, Jean Harlow, and Charlie Chaplin all enjoyed the shimmering waters of the Neptune Pool. The architect Charles Moore described it as a “grand liquid ballroom.” Movie director Stanley Kubrick used it in 1959 as a location for a scene in Spartacus, and Lady Gaga filmed a video there last year.

But the mastermind behind the Neptune Pool -- the architect Julia Morgan -- preferred to remain out of the spotlight. By the time she died in 1957, she had designed an estimated 700 buildings, mostly in California, where she was the first woman in the state to be licensed as an architect. Morgan’s groundbreaking career spanned a major earthquake, the Great Depression, and two world wars. “Drive is what she had, and the most spectacular will,” says Victoria Kastner, Hearst Castle’s official historian. “She was indomitable.”

Though naturally reticent and reluctant to promote herself, Morgan was a bit of a well-mannered renegade. Born into an affluent San Francisco Bay Area family in 1872, she bucked the traditional path for women of the time by attending the University of California, Berkeley, and majoring in civil engineering. (It was the closest thing to a major in architecture, which the school didn’t offer then.) Her mentor, the great Bay Area architect Bernard Maybeck, urged her to continue her studies at his own alma mater, the prestigious, all-male École des Beaux-Arts in Paris.

Morgan took his advice, becoming the first woman to graduate from the École in 1902. After returning to California, she worked for the architect John Galen Howard. By 1904, she had opened her own office, one of the few woman-owned firms in the country. “She came of age at the dawn of the Progressive era, when women were really beginning to feel the frustration of not being able to use the skills they had learned in college,” says historian and Morgan expert Karen McNeill. “She had chutzpah and moxie. This incredibly competitive woman was not going to be deterred from pursuing her dream because she was born with two X chromosomes.”

The widespread myth that Morgan destroyed all of her papers near the end of her career only adds to her mystique. In his book Bay Area Style, author David Weingarten notes her penchant for privacy, calling her “a sort of Greta Garbo of the Bay Region style.” She did ask staff to burn some of her records, but the Julia Morgan Papers at California Polytechnic State University, San Luis Obispo, contain thousands of letters, drawings, and other archival materials. It’s true that she rarely gave interviews or spoke in public, and she disliked being photographed. Really, the best way to get to Julia Morgan is through her work.

In the main building at Asilomar Conference Grounds on the Monterey Peninsula, an extended family plays a board game in front of an enormous stone fireplace. The quiet crackle of the fire and the sharp, rhythmic clicks coming from the pool tables on the other side of the room underlie the low conversations of hotel guests. Big glass windows dominate the redwood walls, framing views of the rolling, pine tree–dotted landscape. Twenty-eight feet overhead, an exposed redwood ceiling and trusses provide a reassuring sense of enclosure. It would be hard to feel anxious or uncomfortable in this building, known as Phoebe Apperson Hearst Social Hall.

Morgan’s design for the Social Hall was built in 1913 as part of Asilomar, a YWCA conference camp. Her reputation as a go-to architect was already secure, thanks to her Mills College bell tower and library in Oakland, which stayed intact through the devastating San Francisco earthquake of 1906. “When both buildings survived, it catapulted Julia Morgan into the upper echelon of Bay Area architects,” says Karen Fiene, the campus architect at Mills. Even before that, Morgan’s work had attracted the attention of philanthropist and Social Hall namesake Phoebe Apperson Hearst, who hired Morgan to remodel her estate in Pleasanton, California.

Hearst also recommended Morgan to the YWCA, which would remain an important client for the rest of her career. She designed at least 30 YWCA buildings, mostly in California, but Asilomar is the crown jewel. The 107-acre beachside site is now one of the highest-grossing parks in the California state parks system. (Hearst Castle is the highest.) Eleven of Asilomar’s 60 current structures were created by Morgan between 1913 and 1928, and each one seems like a handmade piece of furniture.

They’re not complicated, mind you—on the surface, they couldn’t be more different from lavish Hearst Castle. Built in the simple Arts & Crafts style out of redwood and stone, they defer to their natural backdrop of coastal splendor, just over the hill from world-famous Pebble Beach. But Morgan used the same basic principles in all of her work, some derived from her rigorous Beaux-Arts training and some just from her own convictions. She designed around a natural landscape, leaving trees in place when possible and letting views help determine building placement. At Asilomar, the shingled Stuck-up Inn (housing for a group of college students who worked at the camp over the summer and called themselves “The Stuck-ups”) wraps around a courtyard shaded by the canopies of three coast live oak trees. A few minutes’ walk away is the Chapel, where the entire west wall opens up to take in the dunes outside and the soft roar of the ocean beyond.

“The brilliance of Julia Morgan is that the buildings feel natural and fitting with the environment,” says Lada Kocherovsky of Page & Turnbull, which along with its work on the Neptune Pool also restored the Social Hall at Asilomar in 2012. “She maintained the energy and serene character of the site. The landscape feels untouched.”

In 1956, Asilomar, including its buildings and its beach, was declared a unit of the state parks system. A master plan by the architect John Carl Warnecke, who also designed John F. Kennedy’s gravesite, has helped the place retain its fragile tranquility, even with the addition of other buildings. With 312 hotel rooms and several large meeting spaces, it’s a popular spot for travelers, corporate retreats, and conferences. When you check in, you receive a map highlighting the Morgan buildings, which were listed on the National Register of Historic Places in 1987. A century after she first began designing there, Julia Morgan’s work still resonates.

Not only did Phoebe Apperson Hearst help introduce Morgan to the YWCA, she also is believed to have connected the architect with her son, newspaper magnate William Randolph Hearst. When he decided to build a Japanese-influenced bungalow on his sweeping property above the Pacific in central California, he tapped Morgan. Soon he changed his mind about the bungalow and instead envisioned a Mediterranean Revival-style castle.

This pattern continued for the next 20-plus years of their collaboration on Hearst Castle; Hearst constantly asked for changes, which most architects detest, and Morgan took it in stride. “I will do my very best to keep the cost down, but as you know, both the times and the local conditions are full of uncertainties,” she wrote to him presciently in September 1919.

She would expertly tweak the plans when he suddenly opted to add a wing or, say, enlarge the Neptune Pool, which happened twice after its initial construction in 1924. “You can tell she was really fast on her feet when things would change,” says Page & Turnbull’s Tom Dufurrena. Morgan’s organized, disciplined mind helped her to stay ahead of Hearst’s whims.

As a result, the castle is the highlight of the state parks system, attracting 750,000 visitors a year from all over the world. (The 1941 movie Citizen Kane, very loosely based on Hearst’s life, also helped make Hearst Castle famous, although it wasn't filmed there and takes many liberties with the facts.) Morgan and Hearst worked on the project together for more than two decades, starting at a time when, as Kastner points out, Morgan didn't even have the right to vote in national elections. She would often take the night train down from San Francisco and then be driven more than an hour up a winding dirt road to the hilltop estate, which Hearst called “La Cuesta Encantada.”

Morgan tended to de-formalize even the most formal of spaces, lending this dramatic castle filled with antiquities a surprisingly intimate air. There is no grand staircase or imposing foyer at Hearst Castle. Instead,a tiled entryway leads directly into the paneled Assembly Room, once used for dancing and, on quieter nights, card games around the hearth. Fireplaces were a favorite detail of hers—Hearst Castle has 30 of them in the main building alone.

She loved pools, too. As a counterpart to the Neptune Pool, Morgan also designed the Castle’s cerulean Roman Pool, a showstopping indoor swimming area that might as well have been rescued from the lost city of Atlantis. Almost every surface is covered with Italian-inspired mosaics made from 1-by-1-inch Venetian glass tiles, some infused with 22-karat gold. Marble ladders curl up from the water’s gleaming surface like seahorses, while alabaster lamps emit a ghostly glow. It’s a space of pure delight designed by an unfettered imagination and built by the world’s best craftsmen, and no one who sees it forgets it. “The Roman Pool shows what Julia Morgan could do when she didn’t have to design around all those changes,” says Kastner.

While the Hearsts and the national YWCA board were certainly powerful clients, Morgan was just as skilled at designing for people with fewer resources. One of her best buildings is the Chinese YWCA in San Francisco, now owned by the Chinese Historical Society of America. Built relatively late in her career, in 1932, it shows a cultural sensitivity unusual for the time. Morgan researched the meanings of traditional Chinese symbols -- infinity and longevity knots, chrysanthemums, and bats for good luck -- and had them hand-painted in each square of the entry’s coffered ceiling. Red-painted interior woodwork, carved screens on the front doors, and gold latticework around the reception area all provided additional cultural touchstones for the YWCA’s patrons, mostly Chinese women and children.

“The inclusion of all the Chinese motifs is just amazing,” says Sue Lee, the historical society’s executive director. “This feels so much more authentically Chinese than the Chinatown pagoda tops.” Morgan waived her fee for the building, which also includes a gymnasium and office space. The gym, where the children learned American sports as part of their families’ efforts to assimilate, is now used for exhibitions and gatherings. “We find that the gym is a fabulous meeting space,” Lee says. “It makes you feel like you’re part of something bigger, but it’s not intimidating.”

The Chinese YWCA and Berkeley City Club, a women’s club near the university, were two of Morgan’s last high-profile projects. She kept designing buildings for the Hearst family and other private clients until the late 1940s, when she closed her office in the Merchants Exchange Building in downtown San Francisco. Modernism was the rage, and her eclectic style had fallen out of fashion.