The book revolves around two modernist opera theatres-designed by two leading female architects-that stand on the Soviet periphery, in Lithuania and Belarus: the Opera and Ballet Theatre in Vilnius (1962-74) by Nijole Buciute and the Comic Opera in Minsk (1973-81) by Oxana Tkachuk. The book reconstructs the history of how each theatre was commissioned, planned, and built; it also uses their contextualization as a means to examine the contemporary political and cultural events that had been unfolding on the stages of the Republics prior to and at the time of the theatres' creation. The book looks at how modernist architecture co-created and conveyed the self-imaginaries of the "new nations" of Belarus and Lithuania. By addressing the long-neglected processes of nation-building within the Soviet Union and the way built environments were involved in this, it helps comprehend the forces that propelled the Soviet Union towards its collapse, while placing architecture's entanglement with them centre stage. Oxana Gourinovitch, PhD TU Berlin, is an architectural historian, architect, and curator. The publication is based on her PhD thesis, which was awarded the Tiburtius Prize in 2021. The publication is supported in part by the Graham Foundation's publishing grant.