But it wasn’t paradise. Tito commanded a fearsome secret police organization. Ethnic, religious, and linguistic tensions never fully disappeared. The books in that glorious Pristina library were censored; so was the work in Belgrade’s Museum of Contemporary Art, on display as a model here. At MoMA you will see a slide show of mod beach resorts on Croatia’s fashionable coast, by local architects and even by Edward Durell Stone, who designed MoMA’s first building. What you won’t see is the island that housed political prisoners offshore.

One of the main focuses of Yugonostalgia today is the hundreds of spomeniks, or memorial monuments, most built to commemorate the victory over Fascism and to honor the one million Yugoslavs killed in World War II. In contrast to the Socialist Realist gigantism elsewhere in the East (think of “The Motherland Calls,” the 280-foot swordswoman who towers over Volgograd, Russia), these concrete spomeniks aimed to unify multiethnic Yugoslavia through futuristic abstraction. One Bosnian monument dramatizes a siege using concrete blocks grouped around a hollow cylinder. Another, which Mr. Jeck has photographed under a blanket of snow, comprises two massive chevrons that edge together, then shear apart.

For better or worse the show cuts off at 1980: before the Winter Olympics of 1984, and before the breakup of the country that brought the world’s attention to Sarajevo for much grimmer reasons. Yet “Toward a Concrete Utopia” offers an oblique coda to this age of construction through an excerpt from “A Hole in the Head,” a 2016 documentary film by the Slovak director Robert Kirchhoff. We see three men standing in the snow beneath one of these Socialist relics in Croatia, a huge concrete flower on the site of a Fascist-run death camp where tens of thousands of Serbs, Jews and Roma lost their lives during World War II. The men walk toward the monument, talking of the horrors that arise when one group considers another to be less than human. But maybe they are not talking about World War II. Maybe they are talking about the massacres to come, of people that one character calls “not worthy to be counted.”

I spent a while looking at a map here, made in 1975, that pinpoints hundreds of these anti-Fascist monuments, scattered evenly across borders the cartographer had no idea would rise again. By a river in the east of Bosnia I found a marker of a spomenik in the shape of a broad cube, and the name of the nearby mountain town: Srebrenica, site of the worst massacre in Europe since World War II. The land beneath these concrete towers is blood-soaked, and perhaps it is no surprise that Croatia’s footballers did not draw much support from neighboring countries. But before the wars and the splintering, there was a grander future in view, molded in glass and concrete.