For eight years in the 1960s, the Italian architect Carlo Mollino designed a hidden apartment on the first floor of a nineteenth century villa in the heart of Turin for himself in secret. The eclectic, if not downright enigmatic, property is a monument of Mollino’s three obsessions: sex, death, and ornate furniture.

If you’ve ever been curious where real genius resides, head to the disheveled apartment that lives inside an eighteenth-century palazzo beside Parco Sempione, where Achille Castiglioni, one of the twentieth century’s greatest designers, lived, worked, and smoked cigarettes from 1944 until his death in 2002. The drawings, prototypes, material samples, and research books cluttering the studio’s four rooms are just as Castiglioni left them during his packed days creating Toio lamps.

The best time to visit the historic house and library once belonging to the neoclassical architect Sir John Soane is after dark. Come night, the museum lights are dimmed and the dizzying collection of antique curios and interwoven rooms are illuminated solely by a constellation of small spotlights.

When minimalism so often equates to sterile design defined by negative space, the Eames House in Los Angeles remains a peerless example of bold pragmatism. Easily one of the most influential homes of the 20th century, the property was assembled by Charles and Ray Eames in a eucalyptus grove in Pacific Palisades in 1949 with Ikea-like efficiency from readymade panels of glass, steel, and stucco.

Before his death in 1990 at the age of eighty-five, George Nakashima, the Japanese-American architect and master craftsman, built a fourteen-building housing complex stretching across eight-point-eight acres of verdant land in New Hope, Pennsylvania. The grounds, where Nakashima’s two children continue to live and offer tours to visitors, are radical studies in Japanese craftsmanship and naturalism.

Last year, on the 150th anniversary of the birth of Italian futurist artist Giacomo Balla, curators at the MAXXI, the National Museum of 21st Century Arts in Rome, opened the doors of Balla’s apartment to the general public. But the house, where he lived from 1929 until the early 1990s with his wife, Elisa Marcucci, and their two daughters, Luca and Elica, is not so much a residence as it is a portal into a parallel universe.

French designer Le Corbusier took a twofold approach to his best known masterpiece, the Villa La Roche and Villa Jeanneret. A pair of white structures built side by side in 1925 in Paris's Square du Docteur Blanche, the deux villas are comprised of one house for the family of Le Corbusier's brother, Albert Jeanneret, and a house for Le Corbusier’s close friend Raoul La Roche, an in-the-now Swiss banker and art-collecting man about town.

Many architects seek to integrate their buildings into their surrounding environment, but few have done so as inventively as Alden Dow. A student of Frank Lloyd Wright before later becoming Wright’s contemporary, Dow possessed a simple design philosophy lifted from his former teacher: “Gardens never begin, and houses never end.” Nowhere was this motto more on display than his own home and studio in Midland, Michigan, which Dow constructed patiently over four stages throughout the 1930s.