More than 1,600 years ago, close to the southeastern coast of the Korean Peninsula, laborers were hard at work building a palace for a fledgling kingdom. They finished the foundation layer of the massive western rampart and then paused before beginning the next construction phase, a stone wall. The foundation, made from packed shells and earth, was complete from an engineering standpoint. But the ancient builders believed something more was needed to protect the structure: human sacrifices. The victims sealed in the rampart included a peasant couple in their 50s,…