The Industrial Revolution didn't hit Germany until the late 19th century. But when it did, it transformed the country almost overnight. Berlin went from 960,000 to 1.89 million people in just 25 years. Public expenditures for housing were minuscule, and by the eve of World War I, unsanitary and overcrowded apartment blocks were the norm for most Germans. In 1924, the government passed a 15 percent tax on rent in previously erected buildings, the proceeds from which went to new construction. Berlin alone saw the addition of 135,000 units, the bulk of them in sprawling housing estates, between 1924 and 1931.

More important than quantity was quality: Built by some of the country's leading architects, the estates reflect the best of the early modernist commitment to design for contemporary urban life. "City planning and reform of the civic body is a critical question of the highest degree," declared architect Martin Wagner, director of the Berlin Building Administration, in 1929.

The estates were immensely popular at the time, and they remain sought-after addresses today. Despite average rents of 5.5 euros per square meter in some of the developments—well above the Berlin average of 4.75 euros—waiting lists are frequent. Six of the estates were added to the UNESCO World Heritage list this summer as "exceptional examples of new urban and architectural typologies, designed in the search for improved social living conditions." But as models for how mass housing can be built efficiently and work effectively, they have long been overlooked by governments that prefer short-term savings, even at the cost of the long-term social ills that come with bad public design. It's time for that to change.

Weimar architecture is largely thought to begin and end with the Bauhaus. But in terms of built work, the interwar city housing authorities, responsible for hundreds of projects a year, were the real center of German architecture. Most of the projects were funneled through nonprofit building cooperatives, a decentralized approach that guaranteed a diversity of styles and solutions. While several of the country's largest estates were built in a conservative, völkisch idiom, modernism became the de facto style of interwar housing construction. It appealed to the era's progressive mayors and city officials; they saw it as an architectonic version of their own desire for new solutions for the new masses of urban, industrial workers. After setting high standards for quality and amenities—all apartments had running water, toilets, and kitchens—they hired forward-thinking planners like Wagner in Berlin and Ernst May in Frankfurt to carry out their visions; those men in turn hired up-and-coming architects like Hans Scharoun, Bruno Taut, and Walter Gropius.

Perhaps the most famous of the Berlin projects is Taut's Hufeisensiedlung, or Horseshoe Estate, so-called because the centerpiece is a three-floor apartment building in the shape of a 1,150-foot inverted U. At the horseshoe's center lies a tree-flocked pond, and each of the apartments has access to both private garden space and public greens arrayed around the pond's edges. That dense, central block is complemented by more than a dozen rows of two-floor attached row houses loosely ranged around it; each fronts on a narrow road and sports a private garden in back.

Working with a slim budget and a narrow range of materials, Taut nevertheless achieved a striking level of pleasant detailing and softening asymmetries. The apartment rows don't meet the street uniformly, but rather move back and forth to create a variety of spatial settings. He varied brickwork and paint colors. And he arranged the different blocks to maximize social interaction; the center of the horseshoe, combining play areas for children and gardening spaces for adults, becomes an external, communal "room."

Across town, the developers of the Siemensstadt, or Ring Estate, took another approach by drafting young, talented architects to design different takes on the same basic unit, an elongated four- and five-floor block. Built between 1929 and 1934, the project employed Gropius, Scharoun, Hugo Häring, Otto Bartning, and other rising stars of German architecture. Each was free to conceive his own floor plans and access routes, resulting in a stunning array of living spaces within a tightly conceived general plan. All, however, displayed a humane attention to detail that prevented the blocks from sinking into numbing sameness.

Scharoun, charged with creating the zoning plan, brought the same balance of variety within uniformity to the estate's green spaces. "The idea," note preservationist Jörg Haspel and Bauhaus Archive director Annemarie Jaeggi in their book on the estates, "was not the rigid functionalist elongated building; it was a spatial subdivision based on the natural features of the site and including narrower and wider sections, spatial boundaries and extensions, seclusion and openness."

Taken as a whole, the estates are a systematic historical record of modernism's efforts to reconcile urban conformity with the human urge toward individualism and free communal interaction. How do you design a facility that is rational and efficient, but also loose and varied enough in its program to allow for chance encounters and personal expression? Not every answer was the right one, but the continued popularity of the estates makes for a convincing case that many of their designers were on the right track.