Tour buses rolled into Riverside Plaza (formerly Cedar Square West) on Thursday afternoon, disgorging fans and advocates of midcentury and modern design for a walk around the 1970s highrise apartment complex designed by Ralph Rapson.

The tours were part of a national convention called "Modernism on the Prairie," organized by Docomomo and its Minnesota chapter that brought nearly 200 people to town through this weekend. The group, involving architects, designers, historians and preservationists, has been involved in high-profile efforts around the country to preserve and defend mid-20th-century buildings, including ones not universally loved. These designs often don't qualify for designation as historic landmarks under rules stipulating that such buildings must be more than 50 years old.

Riverside Plaza is a bold example of the kind of architecture that's at the heart of Docomomo's mission. Born of late 1960s idealism and built mostly in the early 1970s, the complex had fallen into disrepair by the '00s. Rapson's plan combined a DeStijl color scheme with a brutalist concrete construction and included one building that is the city's tallest outside of downtown. Both tenants and observers tend to have a love-hate regard for the place.

Plazas, a pool and community center at the towers' base were intended to give the residents a sense of community. Parking was mostly tucked below grade, and the complex rises above the busy, cross-cultural West Bank neighborhood near the University of Minnesota, where Rapson ran the architecture department from 1954 to 1984.

The ideal of an urban Utopia in housing soon revealed practical shortcomings. The above photo shows an unsightly elevator shaft that had to be retrofitted on one of the apartment towers to alleviate long waits due to too few elevators servicing the upper stories. Tenants of the 1,300 units, now mostly Somali-Americans, continue to complain about this and other hassles there, including deficiencies in plumbing and wiring. But the complex demonstrates its staying power in the fact that it remains almost fully occupied, with a wait list.

Charlene Roise, president of local consultants Hess Roise, led the Docomomo tour Thursday, telling the mostly out-of-town visitors about the challenge of winning for Riverside Plaza its 2010 listing on the National Register of Historic Places. That helped win historic tax credits in support of a $130 million renovation completed in 2012. The original color scheme has been redone, along with other modernizations that required temporarily moving tenants in a complicated scheme. Riverside Plaza now has an onsite school, grocery and security center.

The complex "was designed to be a community," Roise said in an interview, "and one of the wonderful things about it is that it IS a commnity, and the renovation helped it remain a community."

Roise believes that the stereotypically cold building material Rapson chose has nonetheless been embraced by tenants. "Even though it's this hard concrete shell," she said, "it's marvelous how it has been able to adapt to various people over time."

A new residential project going up to the west of the site is blocking what for years was a terrific downtown view from a stepped concrete plaza at Riverside.

The Rapson tour also stopped at Rarig Center on the U's West Bank, and at University Grove, the bucolic residential area where Rapson designed eight modern homes. Speaking at Rarig were Toby Rapson, son of Ralph Rapson, as well as architect and U professor Kay Lockhart, who worked with Rapson on Rarig ahead of the mammoth building's 1972 opening. Lockhart recalled how "cost engineering" forced cutbacks, resulting in a budget of just $5.5 million for the brick and concrete structure housing Theater Arts as well as radio and television studios in the upper floors. Rarig's thrust theater is a small-scale replica of the famed Guthrie thrust, designed 10 years earlier by Rapson, and now demolished.

At University Grove, two homeowners allowed Docomomo-ists to walk around inside. The Shepherd House (pictured below) has been lovingly restored by its current owner, who combined restoration work with new additions respectful of Rapson's original plan. (Recent story about that renovation is here.)