Modern Marvels: Some of the most imposing structures ever built, medieval castles withstood both bloody assaults and the test of time. Designed like machines with nearly every architectural detail devoted to defense, castles represented the perfect fusion of form and function. Journey back to that unruly era as we examine the complexity of their construction and the multipurposes they served--homes to kings and nobles, economic centers, courthouses, treasuries, prisons, and torture chambers.