Deep beneath the city of Rzeszów, Poland, lies a relic of the Cold War—the Marysieńka Shelter. Once a secret refuge designed to protect against nuclear fallout, this underground bunker remains largely unknown to the outside world. In this ON-LOCATION episode of It's History, we tour the eerie corridors and abandoned rooms of this historic shelter to uncover what still remains. Join us as we explore the bunker’s past, from its construction during the Cold War to its present-day condition. We examine the architecture, survival provisions, and Cold War technology left behind. What was this place built to withstand? And why has it been forgotten? Step inside Poland’s hidden history and discover the secrets beneath Rzeszów.