A 250-kilometer fence of barbered wire acts as a divider between the two worlds of Korea. In the north, a harsh dictatorship demands socialist-realist painting. In the democratic south, artists are free and full of contemporary vitality. Uli Sigg, the Swiss ambassador to North Korea from 1995 to 1998, was one of the few westerners to penetrate the armored country. During his time there he collected paintings, while developing a unique insight into art created as propaganda. “Border Crossings,” which features work that Sigg acquired in both North and South Korea, is a window into parallel yet drastically different lives. —E.C.