Milton Gendel was waiting by the open door of his apartments in Palazzo Primoli, not far from Piazza Navona, in Rome, when I stopped by for a first visit, in 2011. His slender frame was angled comfortably against the doorframe, the pose of a younger man. He was already 92.

During the seven years he had left, I saw him three or four times a year, whenever I was in Rome. We had been introduced by a mutual friend, which in Gendel’s case could have been almost anyone. His range of friends and acquaintances was wide, his capacity for extending it unconstrained.

To know Gendel was to achieve one degree of separation from an improbable array of characters. Some are people you’ll have heard of: Diana Cooper, Mark Rothko, Princess Margaret, André Breton, Robert Motherwell, Anaïs Nin, Gianni Agnelli, Gore Vidal, Martha Gellhorn, Alexander Calder, Muriel Spark … and a thousand more like these. Others are people who have left no public footprint but with whom he was just as happy to spend his time—the ordinary Romans he lived among for seven decades, from his arrival in the city, in 1949 at the age of 30, until his death, in 2018, just two months shy of his 100th birthday.

Milton Gendel was a photographer, a critic, a sounding board, a facilitator, a convener, a collector. Asked why he had chosen to spend his life in Rome, he would generally reply that he was “just passing through,” which is what everybody is doing in Rome, whether they know it or not.

To know Gendel was to achieve one degree of separation from an improbable array of characters.

His various homes in the city were certainly a destination for others passing through—writers and artists, actors and journalists, aristocrats and arrivistes and members of what used to be called the jet set. It was a long 20th-century moment that will someday have a name, with the ancien régime still palpable in its twilight but so much else upended or made new.

Privately, Gendel was a diarist, leaving behind daily entries totaling some 10 million words. The diaries cover everything from mundane details of Gendel’s family life to accounts of his travels and observations about books, movies, and the arts. Meticulously, they also memorialize the scene, and the conversation, at numberless intimate gatherings. From time to time he would pull out a few pages to show me. We talked about the idea of publishing a selection one day, together with some of his photographs—a project that has at last come to fruition, under the title Just Passing Through. The book will be published next week.

Gendel was a superb writer, with an ear for the sharp as well as the absurd, a sly sense of humor, and a gift for decisive assessment. (The sex scenes in Zabriskie Point, he writes in one entry, bring to mind “coupling dogs trying to obey the laws of the Stanislavski method.” The painter Balthus, he writes in another, resembles “a lizard with a high IQ” whose slow, deliberate speech “gives even banalities a certain weight.”)

At the same time, he was personally unobtrusive. That angled pose in the doorway, watching my approach, captures something of his manner. In a Sargent painting, he might be the shadowy figure in the background, the one you wonder about.

One way to get an immediate feel for the man was to pass through the heavy wooden doors into the suite of rooms that took up most of the piano nobile of the Palazzo Primoli. He had only recently moved in when I arrived—he had lost a previous apartment, in the Palazzo Doria Pamphilj—and was still unpacking, but the walls were already hung with paintings (modern, Baroque), and the shelves already sagged with his books. Still unpacked were a lifetime of photographic negatives waiting to be catalogued, and the library recently left to him by Cesare D’Onofrio, the noted historian of Rome.

Every horizontal surface—floors, tables, windowsills—held objects collected over a lifetime: Etruscan pottery, Roman marbles, medieval carvings, crèche figures from Naples, bas-reliefs in bronze, commemorative medallions, coins and medals, candlesticks, masks, Judaica.

For decades, Gendel made a weekly pilgrimage to the flea market at Porta Portese. On a desk, nestled on a wooden concavity to prevent its rolling, sat a cannonball recovered from the breach of the Aurelian Walls, in 1870, when the forces of Italian re-unification overcame the last resistance of Pope Pius IX. In a bedroom, a pair of shoes had been framed and hung on the wall, the soles facing outward. Once, years earlier, Gendel had accidentally walked on some wet white paint; when he put his feet up one evening, his friend Alexander Calder had seen an opportunity and drawn a wiry portrait of Gendel on each surface, one in profile and one full face.

In time, I came to know Gendel’s wife of nearly 40 years, the artist Monica Incisa della Rocchetta, and his daughter Anna Mathias (with Judy Montagu, Gendel’s second wife). I also came to appreciate, firsthand, Gendel’s peculiar magnetism. He was, as Anna once described him, “his own cultural microclimate.” There was hardly a subject one could mention about which he lacked knowledge—ancient tombs, modern politics, gallery prices, romantic entanglements, Renaissance history, Victorian literature, local genealogy—and yet he was never the first to bring a subject up. He had a way of steering conversations while seeming to be in the passenger seat.

Looking back on the century of his life, it is hard to discern anything like an overt strategy. Some people are visibly driven in a particular direction. They conduct their affairs like a high-stakes chess match. Gendel was deliberate and serious about many things, quick to seize opportunities, and sometimes insistent about aesthetic decisions; but following a master plan was not part of the repertoire.

Over lunch one day across the street from Palazzo Primoli, Gendel’s longtime friend Barbara Drudi, a scholar and critic, put it this way: “He had a kind of good fortune. He never pushed his destiny. He never searched for success. And something happened anyway.”

“His Own Cultural Microclimate”

Milton Gendel, the son of Jewish immigrants from Russia, was born in New York City on December 16, 1918. Gendel always thought of himself as a New Yorker, even after seven decades in Rome. He attended Columbia University as an undergraduate and then, with his friend Robert Motherwell, stayed on to pursue a master’s degree in art history. His mentor, for whom he worked as an assistant, was the legendary art historian Meyer Schapiro.

In the late 1930s and early 40s, the New York art scene had been both fortified and turned upside down by the arrival of the Surrealists—airlifted (literally) from war-torn Europe by the collector Peggy Guggenheim—and Gendel was soon immersed in this world. With Motherwell, he was invited to join the staff of André Breton’s Surrealist magazine VVV, and the apartment he shared with his girlfriend (later his first wife), Evelyn Wechsler, at 61 Washington Square, became an artistic and social hub.

What brought this life to an end—for Gendel, though not for others in this Greenwich Village circle—was America’s entry into the war. Gendel believed he should join the fight, and in 1942 he enlisted in the army. The decision caused a rupture with Breton, who told him, “Vous voulez participer à cette bêtise, mais je dois dire que ça c’est con.” (“You want to take part in this stupidity, but I must tell you it’s idiotic.”)

Joining the army would prove decisive, though not in a predictable way. After attending language school at Yale, Gendel was sent to China, where in 1945 and ’46 he assisted with the repatriation of Japanese soldiers. It was there, with a borrowed Leica, that he began taking photographs, chronicling ordinary life in Chinese cities.

Returning to New York, he worked briefly as a writer for Funk & Wagnalls New Encyclopedia—his archivist impulses getting a thorough workout—while applying for a Fulbright scholarship to take him back to China. He won the Fulbright, but by then China’s civil war had culminated in the victory of Mao Zedong’s Communists. Access was no longer possible for an American. Gendel decided to go to Rome instead, where he would study Italian architecture as it had developed in the period after re-unification.

Gendel had been in Rome once before, when he was 20, as Europe was spiraling into war. He returned with Wechsler in December 1949.

Not long after their arrival, Wechsler met the novelist and essayist Sybille Bedford—whose ramshackle apartment, near the Spanish Steps, Gendel had helped to rewire—and began a long affair. Her marriage to Gendel came to an end. Wechsler eventually returned to New York and became a literary agent and book editor. She and Gendel remained friends.

“He had a kind of good fortune. He never pushed his destiny. He never searched for success. And something happened anyway.”

The Fulbright ended in 1951, but Gendel stayed on. He had picked up Italian—a very good, precise Italian, though he always spoke it with an American accent—and was gradually becoming embedded in Rome. His influential architect friend Bruno Zevi had introduced him to Adriano Olivetti, the industrialist and social visionary, and Olivetti took him on as his English-speaking public-relations adviser.

Gendel also turned his hand to translation, starting with Zevi’s book Saper Vedere l’Architettura, which would eventually be published in English under the title Architecture as Space. Meanwhile, he was writing for ARTnews about modern painters in Italy such as Alberto Burri and Toti Scialoja; eventually he became the magazine’s official Rome correspondent.

Gendel was never a professional photographer or a photographer with a capital P. He admired and was influenced by—and wrote about—Henri Cartier-Bresson, but he did not take photographs in order to have them shown in public (though he showed them to his friends), just as he did not keep his diaries for public consumption.

He had started traveling with his Rolleiflex camera soon after arriving in Rome—making trips to Sicily and elsewhere—and the camera became an adjunct to his life. He stopped taking pictures only in his last years, because his hands sometimes shook, making even the large glass of whiskey he enjoyed in the evening a challenge.

Gendel took photographs for the same reason he kept diaries: in order to remember and record. He was a quintessential observer, led as much by the eye as by the ear. He organized and filed his negatives and contact sheets with care. Once a year he would gather a selection of prints and arrange them on heavy, beige cardboard stock, one spread after another, writing names and locations underneath by hand. Then he would bring the loose pages to a bookbinder, along with the leather to use for covering the boards, and have a bound volume created to his specifications.

In his last years, he continued to see visitors and to write and was often assisted by his grandson Bartolomeo, who was able to run errands, keep filing up to date, and handle issues with the computer. Gendel would take a bus in the morning to Palazzo Primoli from the home he shared with Incisa, in the Ostiense neighborhood of Rome, near the Pyramid of Cestius and the Protestant Cemetery.

Gendel had started traveling with his Rolleiflex camera soon after arriving in Rome and the camera became an adjunct to his life.

After the end of his marriage to Wechsler, Gendel fell in love with Vittoria Berla Olivetti, who was briefly married to Adriano Olivetti’s son, Roberto. Gendel and Berla Olivetti had two children, the twins Sebastiano and Natalia, born in 1958.

But when Gendel re-married in 1962, it was to someone else he had begun seeing: Judith Venetia Montagu, whose British lineage was old and distinguished. (Martha Gellhorn used a fanciful version of this triangle as the grist for her 1961 novel, His Own Man, set in Paris, not Rome, and with the bohemian Sinologist Ben Eckhardt in the role of a young man torn between two very different women.)

Judy Montagu was well connected and close to Princess Margaret. Other friends included Bindy and Tony Lambton, Patrick Leigh Fermor, Pamela Egremont, John Julius Norwich, and Rory and Romana McEwen. Gendel’s own friendships with such people would continue after Judy’s death, in 1972.

In the diaries, mentions of Monica Incisa della Rocchetta eventually begin to appear. There is a passing reference to an encounter in 1970, when Incisa tells Gendel she is working for Merrill Lynch. “Thought she was saying Mary Lynch,” Gendel wrote, “like Fanny Farmer, and couldn’t imagine what sort of brokerage that might be.” A friendship deepened, and in 1981, Gendel and Incisa were married at the Connecticut home of Cleve and Francine du Plessix Gray.

Today, Gendel’s diaries, the most detailed source of information about his life and circle, remain in the hands of his family. The diaries, which depict Rome in one era as intimately as those of Samuel Pepys depicted London in another, will get their scholarly due one day.

The day before he died, Milton was alert and talking about a typo in an article he had just read in The New Yorker. Monica sat with him as he fell asleep. She remembers altering the pattern of her own breathing, slowing it down to synchronize with his.

Cullen Murphy is an editor at large for The Atlantic and the author of several books, including God’s Jury and Cartoon County. Just Passing Through will be published on November 8